Backrest for bariatric chair

ABSTRACT

A chair comprising a base frame; a seat coupled to the base frame and including a seating surface; and a backrest coupled to either the base frame or the seat, including a backrest front surface, the backrest front surface including: an upper backrest front surface including an upper backrest front surface portion; and a lower backrest front surface including a lower backrest front surface portion; wherein the upper backrest front surface portion is disposed, or is positionable to be disposed, forwardly of the lower backrest front surface portion by a horizontal distance of at least 3 inches; and wherein each of the upper backrest front surface portion and the lower backrest front surface portion is disposed in a vertical plane having a vertical plane normal axis which is perpendicular to a normal axis of a plane tangent to the most forwardly disposed front surface of the backrest front surface.

FIELD OF THE INVENTION

This invention relates to chairs for use by overweight persons and, inparticular, to the design of backrests for such chairs.

BACKGROUND OF THE INVENTION

Unlike a person of regular stature and proportion, a bariatric patientoften has an abundance of flesh around the lower torso (e.g. hip, waist,buttocks, thighs, etc.) which protrudes outward from the perimeter ofthe lower body. Due to this additional flesh on bariatric patients, thetypical backrest designs used on most chairs that provide adequatesupport for the general adult population are inadequate for bariatricpatients. Since the extra flesh around the lower torso of bariatricpatients occupies and bottoms-out on the lower backrest, the occupant ispushed forward and upwards. This produces an unsupported gap between theupper torso and the upper-backrest and also between the lower thighs,behind the knee, and the leading edge of the seat.

In the case of non-tilting and non-reclining chairs, which encompasscurrently available bariatric shower and commode chairs, most designsincorporate a backrest which does not provide lower back support andonly provides a narrow backrest supporting the upper lumbar region. Thedisadvantages of this design is that often the excess flesh of thebariatric patient wedges into the opening of the lower backrest makingit uncomfortable for the occupant while sitting, as well as making ituncomfortable for the occupant to exit the chair. These issues areexaggerated even more when the open lower backrest design is used ontilting and reclining positioning chairs. This is because, when tiltedand reclined, the occupant is pulled into the rear of the backrest andseat thus compounding the wedging effect of the lower torso into thatbackrest space even further. In addition, this type of backrest designcreates a potential fall hazard. Even when upright, a bariatric occupantin a chair with a backrest that only supports the lumbar region, anddoes not support the upper back, must exert themselves so as not torelax their posture and lean back too far to keep them from falling overthe top edge of the backrest. There is also psychological anxiety issuesassociated with bariatric chairs with backrests with only a lumbarsupport. Although many bariatric chairs are tested and qualified to holdpatients in excess of 700 lbs, the bariatric patient the chair isintended for may not perceive the chair to be sufficiently safe to sitin, either because of the chair's insubstantial appearance or from thelack of security and support the chair provides once seated.

On tilting and reclining bariatric chairs typically used for loungeseating (ie. non-shower and non-commode chairs), the typical solutionhas been to use heavily padded backrest upholstery thereby allowing anyexcess flesh to be accommodated by the passing and this allowing theentire back to be supported. However, the problem with this solution hasbeen that padding is prone to bottoming out, meaning that when thepadding is compressed excessively, it will not provide uniform support,especially in areas where parts of the occupant may be forced up againstthe rigid structural core of the backrest. In addition, since paddingusually consists of thick foam it does not allow heat or moisture toescape. This is not only uncomfortable, but in conjunction with anyexcessively high pressure points, will eventually lead to pressure sores(ie. decubitus ulcers) if the occupant is left in that position forprolonged periods of time. Also, on a practical-level, heavily paddedsurfaces do not lend themselves to shower and commode applications sincethey create a potential for infection risk due to the possibility forfluids to stagnate in and around padded interfaces. As well, thickpadding is prone to covering much of the occupant's skin therebyobstructing access to different parts of the body to clean and washadequately.

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there isprovided a chair comprising a base frame; a seat coupled to the baseframe and including a seating surface; and a backrest coupled to eitherthe base frame or the seat, including a backrest front surface, thebackrest front surface including an upper backrest front surfaceincluding an upper backrest front surface portion; and a lower backrestfront surface including a lower backrest front surface portion; whereinthe upper backrest front surface portion is disposed, or is positionableto be disposed, forwardly of the lower backrest front surface portion bya horizontal distance of at least 3 inches; and wherein each of theupper backrest front surface portion and the lower backrest frontsurface portion is disposed in a vertical plane having a vertical planenormal axis which is perpendicular to a normal axis of a plane tangentto the most forwardly disposed front surface of the backrest frontsurface.

In accordance with another aspect of the present invention there isprovided a chair comprising a base frame; a seat coupled to the baseframe and including a seating surface; and a backrest coupled to eitherthe base frame or the seat, including a backrest front surface, thebackrest front surface including an upper backrest including an upperbackrest front surface having an upper backrest front surface segment,wherein the upper backrest front surface segment has a width of at least24 inches; and a lower backrest including a lower backrest frontsurface; wherein each portion of the upper backrest front surfacesegment is disposed with a respective portion of the lower backrestfront surface in a respective vertical plane having a vertical planenormal axis which is perpendicular to a normal axis of a plane tangentto the most forwardly disposed front surface of the backrest frontsurface; and wherein each portion of the upper backrest surface segmentis also disposed, or is positionable to be disposed, forwardly of therespective portion of the lower backrest front surface by a horizontaldistance of at least 3 inches.

In accordance with yet another aspect of the present invention there isprovided a chair comprising a base frame; a seat coupled to the baseframe and including a seating surface; and a backrest coupled to eitherthe base frame or the seat, including a backrest front surface, thebackrest front surface including an upper backrest front surface; alower backrest front surface; and a merged front surface, wherein anupper backrest front merging surface of the upper backrest front surfaceextends upwardly from the merged front surface, and a lower backrestfront merging surface of the lower backrest front surface extendsdownwardly from the merged front surface such that the upper backrestfront surface merges with the lower backrest front surface at the mergedfront surface; wherein each of a portion of the upper backrest frontmerging surface, a portion of the merged front surface, and a portion ofthe lower backrest front merging surface is disposed in a vertical planehaving a vertical plane normal axis which is perpendicular to a normalaxis of a plane tangent to the most forwardly disposed front surface ofthe backrest front surface; and wherein an upper backrest front mergingsurface portion plane is tangent to the upper backrest front mergingsurface portion and a lower backrest front merging surface portion planeis tangent to the lower backrest front merging surface portion, whereinthe upper backrest front merging surface portion plane has a front facewhich defines a first angle relative to and above the lower backrestfront merging surface portion plane, wherein the first angle is greaterthan 10 degrees, and wherein the merged front surface portion isdisposed forwardly, or is positionable to be disposed forwardly, of aportion of the lower backrest front surface by a horizontal distance ofat least 3 inches, wherein the lower backrest front surface portion isdisposed in the vertical plane.

According to yet another aspect of the present invention there isprovided a chair comprising a base frame; a seat coupled to the baseframe and including a seating surface; and a backrest coupled to eitherthe base frame or the seat, including a backrest front surface, thebackrest front surface including an upper backrest front surface; alower backrest front surface; and a merged front surface including amerged front surface segment, wherein an upper backrest front mergingsurface of the upper backrest front surface extends upwardly from themerged front surface and a lower backrest front merging surface of thelower backrest front surface extends downwardly from the merged frontsurface, such that the upper backrest front surface merges with thelower backrest front surface at the merged front surface; wherein eachportion of the merged front surface segment is disposed with arespective portion of the lower backrest front merging surface and witha respective portion of the upper backrest front merging surface in arespective vertical plane, and wherein the respective vertical plane hasa respective vertical plane normal axis which is perpendicular to anormal axis of a plane tangent to the most forwardly disposed frontsurface of the backrest front surface; and wherein the respectiveportion of the upper backrest front merging surface is tangent to arespective upper backrest front merging surface portion plane and therespective portion of the lower backrest front merging surface istangent to a respective lower backrest front merging surface portionplane, wherein the respective upper backrest front merging surfaceportion plane has a front face which defines a first angle relative toand above the respective lower backrest front merging surface portionplane, wherein the first angle is greater than 10 degrees; and whereineach portion of the merged front surface segment is disposed forwardly,or is positionable to be disposed forwardly, of a respective portion ofthe lower backrest front surface by a horizontal distance of at least 3inches, wherein the respective lower backrest front surface portion isdisposed in the respective vertical plane; and wherein the merged frontsurface segment has a width of at least 24 inches.

According to yet another aspect of the invention there is provided achair comprising a base frame; a seat coupled to the base frame andincluding a seating surface; and a backrest coupled to either the baseframe or the seat, including a backrest front surface, the backrestfront surface including an upper backrest front surface; a lowerbackrest front surface; and a merged front surface, wherein the lowerbackrest front surface merges with the upper backrest front surface atthe merged front surface; wherein a merging surface portion of the upperbackrest front surface extends upwardly from a portion of the mergedfront surface, and a merging surface portion of the lower backrest frontsurface extends downwardly from the merged front surface portion, andwherein each of the upper backrest front merging surface portion, themerged front surface portion, and the lower backrest front mergingsurface portion is disposed in a vertical plane having a vertical planenormal axis which is perpendicular to a normal axis of a plane tangentto the most forwardly disposed front surface of the backrest frontsurface; wherein an upper backrest front merging surface portion planeis tangent to the upper backrest front surface merging portion and alower backrest front merging surface portion plane is tangent to thelower backrest front surface merging portion, wherein the upper backrestfront merging surface portion plane has a front face which defines afirst angle relative to and above the lower backrest front mergingsurface portion plane, wherein the first angle is greater than 10degrees; and wherein a merged front surface portion plane is tangent tothe merged front surface portion, and wherein the merged front surfaceportion is disposed, or is positionable to be disposed, above a seatingsurface portion of the seating surface by a distance of at least 8inches, wherein the seating surface portion is disposed in the verticalplane and is also disposed in the merged front surface portion plane.

According to another aspect of the present invention there is provided achair comprising a base frame; a seat coupled to the base frame andincluding a seating surface; and a backrest coupled to either the baseframe or the seat, including a backrest front surface, the backrestfront surface including an upper backrest front surface; a lowerbackrest front surface; and a merged front surface, wherein the lowerbackrest front surface merges with the upper backrest front surface atthe merged front surface, and wherein a merging surface portion of theupper backrest front surface extends upwardly from a portion of themerged front surface, and a merging surface portion of the lowerbackrest front surface extends downwardly from the merged front surfaceportion; and wherein each of the upper backrest front merging surfaceportion, the merged front surface portion, and the lower backrest frontmerging surface portion is disposed in a vertical plane having avertical plane normal axis which is perpendicular to a normal axis of aplane tangent to the most forwardly disposed front surface of thebackrest front surface; and wherein an upper backrest front mergingsurface portion plane is tangent to the upper backrest front mergingsurface portion and a lower backrest front merging surface portion planeis tangent to the lower backrest front merging surface portion, whereinthe upper backrest front merging surface portion plane has a front facewhich defines a first angle relative to and above the lower backrestfront merging surface portion plane, wherein the first angle is greaterthan 10 degrees, and wherein a two-dimensional space is disposed in thevertical plane and is defined or is definable between: (i) the lowerbackrest front surface, (ii) the seating surface, and (iii) the upperbackrest front merging surface portion plane, such that the space has anarea of at least 30 inches².

According to yet another aspect of the present invention there isprovided a chair comprising a base frame; a seat coupled to the baseframe and including a seating surface; and a backrest coupled to eitherthe base frame or the seat, including a backrest front surface, thebackrest front surface including an upper backrest front surface; alower backrest front surface; and a merged front surface including amerged front surface segment, wherein an upper backrest front mergingsurface of the upper backrest front surface extends upwardly from themerged front surface and a lower backrest front merging surface of thelower backrest front surface extends downwardly from the merged frontsurface, such that the upper backrest front surface merges with thelower backrest front surface at the merged front surface; wherein eachportion of the merged front surface segment is disposed with arespective portion of the lower backrest front merging surface and witha respective portion of the upper backrest front merging surface in arespective vertical plane, wherein the respective vertical plane has arespective vertical plane normal axis which is perpendicular to a normalaxis of a plane tangent to the most forwardly disposed front surface ofthe backrest front surface; and wherein the respective portion of theupper backrest front merging surface is tangent to a respective upperbackrest front surface merging portion plane and the respective portionof the lower backrest front merging surface is tangent to a respectivelower backrest front surface merging portion plane; and wherein therespective upper backrest front merging surface portion plane has afront face which defines a first angle relative to and above therespective lower backrest front merging surface portion plane, whereinthe first angle is greater than 10 degrees; and wherein each portion ofthe merged front surface segment is tangent to a respective merged frontsurface segment portion plane, and wherein each portion of the mergedfront surface segment is disposed, or is positionable to be disposed,above a respective seating surface portion by a distance of at least 8inches, and wherein the respective seating surface portion is disposedin the respective vertical plane and is also disposed in the respectivemerged front surface segment portion plane; and wherein the merged frontsurface segment has a width of at least 24 inches.

According to another aspect of the present invention there is provided achair comprising a base frame; a seat coupled to the base frame andincluding a seating surface; and a backrest coupled to either the baseframe or the seat, including a backrest front surface, the backrestfront surface including an upper backrest front surface; a lowerbackrest front surface; a merged front surface including a merged frontsurface segment, wherein an upper backrest front merging surface of theupper backrest front surface extends upwardly from the merged frontsurface and a lower backrest front merging surface of the lower backrestfront surface extends downwardly from the merged front surface, suchthat the upper backrest front surface merges with the lower backrestfront surface at the merged front surface; wherein each portion of themerged front surface segment is disposed with a respective portion ofthe lower backrest front merging surface and with a respective portionof the upper backrest front merging surface in a respective verticalplane, wherein the respective vertical plane has a respective verticalplane normal axis which is perpendicular to a normal axis of a planetangent to the most forwardly disposed front surface of the backrestfront surface; and wherein the respective portion of the upper backrestfront merging surface is tangent to a respective upper backrest frontmerging surface portion plane and the respective portion of the lowerbackrest front merging surface is tangent to a respective lower backrestfront merging surface portion plane, wherein the respective upperbackrest front merging surface portion plane has a front face whichdefines a first angle relative to and above the respective lowerbackrest front merging surface portion plane, wherein the first angle isgreater than 10 degrees; and wherein, a two-dimensional space isdisposed in the respective vertical plane and is defined or is definablebetween: (i) the lower backrest front surface, (ii) the seating surface,and (iii) the respective upper backrest front merging surface portionplane, such that the space has an area of at least 30 inches², andwherein the merged front surface segment has a width of at least 24inches.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the present invention are described below withreference to the accompanying drawings in which:

FIG. 1 is a front perspective view of a bariatric chair having anarmrest assembly according to an embodiment of the present invention;

FIG. 2 is a side elevation view of a bariatric chair having an armrestassembly according to an embodiment of the present invention;

FIG. 3 is a front elevation view of a bariatric chair having an armrestassembly according to an embodiment of the present invention;

FIG. 4 is a rear elevation view of a bariatric chair having an armrestassembly according to an embodiment of the present invention;

FIG. 5 is a top plan view of a bariatric chair having an armrestassembly according to an embodiment of the present invention;

FIG. 6 is a perspective view of an armrest assembly of a chair accordingto an embodiment of the present invention;

FIG. 7 is an exploded perspective view of an armrest assembly of a chairaccording to an embodiment of the present invention;

FIG. 8 is a plan view of an armrest assembly of a chair in a firstnarrow position according to an embodiment of the present invention;

FIG. 9 is a plan view of an armrest assembly of a chair in a wideposition according to an embodiment of the present invention;

FIG. 10 is a plan view of an armrest assembly of a chair in a secondnarrow position according to an embodiment of the present invention;

FIG. 11 is a cross-sectional side elevation view of an armrest assemblyof a chair according to an embodiment of the present invention,illustrating a hand wheel locked in an engaged position;

FIG. 12 is a cross-sectional side view of the armrest of FIG. 11,illustrating the hand wheel locked in a disengaged position;

FIG. 13 is a top perspective view of a backrest of a chair according toan embodiment of the present invention;

FIG. 14 is a side elevation view of a backrest of a chair according toan embodiment of the present invention;

FIG. 15 is an exploded view of a seat of a chair according to anembodiment of the present invention;

FIG. 16 is a front perspective view of a chair frame of a chairaccording to an embodiment of the present invention;

FIG. 17 is an illustration of an extendible/retractable support memberof a chair according to an embodiment of the present invention;

FIGS. 18 and 19 are, respectively, the side elevation view and a frontelevation view of the combined seat and backrest of a chair according toan embodiment of the present invention, illustrating the relationshipbetween various components of the seat and backrest;

FIGS. 20A, 20B, 20C, and 20D are, respectively, a side elevation view, atop plan view, a further side elevation view, and yet a further sideelevation view, of the combined seat and backrest of a chair accordingto an embodiment of the present invention, further illustrating thespatial relationship between the components of the chair and thebackrest;

FIGS. 21, 22, 23 and 24 are, respectively, a side elevation view, a topplan view, a further side elevation view, and a front elevation view ofthe combined seat and backrest of a chair according to an embodiment ofthe present invention, illustrating various points of reference todefine dimensions of the backrest;

FIGS. 25 and 26 are, respectively, a side elevation view and a top planview of a combined seat and backrest of a chair according to anembodiment of the present invention, illustrating the relationshipbetween various components of the seat and backrest to assist indefining the cross-sectional area of a recess provided by the chair;

FIGS. 27, 28 and 29 are, respectively, a side elevation view, a top planview, and a further side elevation view of a combined seat and backrestof a chair according to an embodiment of the present invention,illustrating the relationship between various components of the seat andback rest to assist in defining the depth of a recess provided by thechair;

FIGS. 30, 31 and 32 are, respectively, a side elevation view, a topplane view, and a further side elevation view of a combined seat andbackrest of a chair according to an embodiment of the present invention,illustrating the relationship between various components of the seat andthe backrest in order to assist in defining a depth of a recess providedby the chair;

FIGS. 33 and 34 are, respectively, a side elevation view and a top planview of a combined seat and backrest of a chair according to anembodiment of the present invention, illustrating the relationshipbetween various components of the seat and the backrest in order toassist in defining the height of a recess provided by the chair;

FIGS. 35, 36 and 37 are, respectively, a front elevation view, a topplan view, and a side elevation view of a combined seat and backrest ofa chair according to an embodiment of the present invention,illustrating the relationship between various components of the seat andthe backrest in order to assist in defining the spatial relationshipbetween such components;

FIGS. 38 and 39 are side elevation views of a combined seat and backrestof a chair according to an embodiment of the present invention,illustrating the relationship between various components of the seat andthe backrest in order to assist in defining a depth of a recess providedalong a width segment of the chair;

FIG. 40 is a side elevation view of a combined seat and backrest of achair according to an embodiment of the present invention, illustratingthe relationship between various components of the seat and the backrestin order to assist in defining a height of a recess provided along awidth segment of the chair;

FIG. 41 is a side elevation view of a combined seat and backrest of achair according to an embodiment of the present invention, illustratingthe relationship between various components of the seat and the backrestin order to assist in defining a cross-sectional area of a recessextending along a width segment of the chair; and

FIG. 42 is a bottom plan view of a seating element of a chair accordingto an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, the present invention provides a chair 10 includinga chair frame 12, a seat 14, and a backrest 16. The chair frame 12supports the seat 14 and the backrest 16 upon a reaction surface 8.

Referring to FIG. 16, the chair frame 12 includes a structural framesupported on rolling means. The structural frame comprises two unitaryside structures 900 a, 900 b joined by cross braces 961, 962. Theelements of the structural frame are made of one inch diameter, 16 gauge(ie. 0.065 of an inch wall thickness) stainless steel tubing. Thestructural frame is supported on each side by front casters 100 a, 100 band rear casters 110 a, 110 b, and a wheel 101 a, 101 b intermediate thefront and rear casters. For example, the casters 100 a, 100 b, 110 a,110 b are Tente™ brand five inch diameter stainless steel lockingcasters. For example, the wheels 101 a, 101 b are Colson™ brand eightinch diameter Performa™ wheels with stainless steel axles.

The chair frame 12 includes two unitary side structures 900 a, 900 b.Each of the side structures 900 a, 900 b includes a respective one ofupper rails 90 a, 90 b, a respective one of front vertical members 91 a,91 b, and a respective one of lower rails 93 a, 93 b. Each of the upperrails 90 a, 90 b and each of the lower rails 93 a, 93 b extendrearwardly from a respective one of the front vertical member 91 a, 91 band are joined to a respective one of rear vertical members 911 a, 911 bat the rear of the chair frame 12.

The unitary structures 900 a, 900 b are joined together by cross braces961,962. Spaced apart lowered cross member braces 98 a, 98 b extendrearwardly and downwardly from cross brace 961.

Each brace 98 a, 98 b is pivotally coupled to one end of a respectiveone of a pair of extendible/retractable members 200 a, 200 b (see FIGS.1, 2, and 4) by a respective bolt extending through a respective pair ofaligned apertures, one of the respective pair of aligned apertures beingprovided in a respective one of the braces 98 a, 98 b and the otherbeing provided in a respective one of the members 200 a, 200 b. Each ofthe extendible/retractable members 200 a, 200 b is pivotally coupled ata second opposite end to the seat 14 (see below) by a respective boltextending through a respective pair of aligned aperture, one of therespective pair of aligned apertures being provided in a respective oneof a pair of posts 81 a, 81 b provided on the seat frame 18 (see below)and the other of the respective pair of aligned apertures being providedin a respective one of the members 200 a, 200 b. The members 200 a, 200b support the seat 14 in various positions of tilt.

A lowered cross brace 97 is also provided, extending between and joiningthe unitary structures 900 a, 900 b, and coupled to each of the braces98 a, 98 b. The brace 97 provides additional support to the braces 98 a,98 b which are loaded by the weight of the chair occupant beingtranslated to the extendible/retractable members 200 a, 200 b.

Each of the front casters 100 a, 100 b is coupled to and depends fromthe lower end of a respective one of the front vertical members 91 a, 91b. Each of the rear casters 110 a, 110 b is coupled to and depends froma respective one of the rear vertical members 911 a, 911 b. Each offixed wheels 101 a, 101 b is provided intermediate respective casters100 a, 100 b and casters 110 a, 110 b. Each of the wheels 101 a, 101 bis coupled to a respective one of the upper rails 90 a, 90 b by arespective one of first and second forks 94 a, 94 b and 95 a, 95 b.

The seat 14 is coupled to the chair frame 12. The seat 14 includes aseat frame 18 and a seating element 19 having a seating surface 20. Theseating surface 20 is configured for generally receiving and supportinga portion of the bottom torso of a person occupying the chair (the“chair occupant”). The seating surface 20 can be a continuous or adiscontinuous surface. The seating surface 20 can include discontinuousportions so long as the seating surface 20 performs the function ofproviding the necessary support to the chair occupant. An example of asuitable discontinuous surface is a plurality of spaced apart vinylstraps that are coupled to the seat frame. The plurality of vinyl strapsfunction, in concert, to provide the necessary support to the chairoccupant, and the existence of spaces between the vinyl straps does notnecessarily render the vinyl straps incapable of performing theabove-described function.

In the illustrated embodiment, the seating element 19 is configured topermit the chair occupant to expel bodily wastes into a receivingcontainer 73 disposed below the seat (as further described below). Inthis respect, the seating element 19 includes a centrally positionedopening 22 defined by the seating surface 20 extending from and mergingwith a front edge 24 of the seating surface 20. The front edge 24extends laterally from either side of the opening 22 and merges withside edges 26, 28 of the seating surface 20. The side edges 26, 28extend from the front edge 24 to a rear edge 30 of the seating surface20. The rear edge 30 is disposed opposite to the front edge 24 and joinsthe side edges 26, 28. It is understood that any of the front edge 24,rear edge 30, or side edges 26, 28 can be continuous or discontinuous.In this respect, these edges can include discontinuous portions so longas such edge or edges define the perimeter of a seating surface whichfunctions to provide the necessary support to the chair occupant.

A width of the seating surface 20 is defined as any distance of theseating surface 20 (including any discontinuous portions of the surface20) between the side edges 26, 28 and along any vertical plane parallelto a vertical plane that is tangent to the most forwardly disposedsurface of the front edge 24. A length of the seating surface 20 isdefined as any distance of the seating surface 20 (including anydiscontinuous portions of the surface 20) between the front edge 24 andthe rear edge 30 and along any vertical plane having a transverse axisthat is perpendicular to the normal axis of a vertical plane tangent tothe most forwardly disposed outermost surface of the front edge 24.

The seating surface 20 includes a seating surface portion having aminimum width and a minimum length. In this respect, the width and/orthe length may not be consistently the same for the entire seatingsurface portion but, rather, may vary between a minimum and a maximum.For example, the minimum width is 27 inches and the minimum length is 22inches. As a further example, the minimum width is at least 18 inches,and the minimum length is at least 20 inches. In yet a further example,the minimum width is between 18 inches and 38 inches, and the minimumlength is between 16 inches and 24 inches.

For example, the seating element 19 is constructed with blackpolyurethane foam molded over a medium density fiberboard structuralinner core. It is coupled to the seat frame via four polyurethane foamlocating bosses 2002 a, 2002 b 2003 a, 2003 b and a front locatingflange 2001 (see FIG. 42) that are molded on the underside of theseating element 19 and are configured for alignment with the structuralelements of the seat frame 18 to prevent the seat from sliding relativeto the seat frame 18. The seat remains positioned on the seat regardlessof shifts in weight because the foam locating bosses mate with thestructural elements of the seat frame and, because of the frictioncreated by the weight of the occupant bearing down on the foam seat andthe seat frame. As long as the planar force created by the shift inweight of the occupant does not exceed the combined shear threshold ofthe locating bosses and the interface friction between the foam seat andthe seat frame, then the seat remains substantially stationary.

Referring to FIG. 15, the seat frame 18 is made of one inch square, 16gauge (ie. 0.065 of an inch wall thickness) stainless steel tube andincludes a pair of unitary side structures 800 a, 800 b, each coupled toa respective one of the sides of a main support structure 700. The mainsupport structure 700 includes a tube structure 77 for supporting theseating surface 20 and the receiving container 73. The tube structure 77is shaped to facilitate unobstructed communication between an opening 22(defined by the seating surface 20) and the receiving container 73vertically aligned with the opening 22. The main support structure 700includes a pair of spaced apart posts 82 a, 82 b for pivotal coupling ofa legrest 300 thereto by a pair of bolts, each of the bolts extendingthrough a respective pair of aligned apertures, one of the respectivepair of aligned apertures being provided in a respective one of posts 82a, 82 b and the other of the respective pair of aligned apertures beingprovided in a respective one of an opposing pair of portions of thelegrest 300. The main support structure 700 also includes u-shapedmembers 78, 79 provided for effecting support of the receiving container73. The u-shaped members 78, 79 are coupled to and depend below the tubestructure 77 in spaced apart relation to each other. Tube end caps 88are provided to close the apertures of the tube structures.

In the illustrated embodiment, the receiving container 73 is in the formof a bed pan having a peripherally extending lip 731 with notches 732for engaging a resilient container support structure 72. The containersupport structure 72 is, for example, a 3/16 of an inch diameterstainless steel rod formed and welded to the desired shape. Thecontainer support structure 72 is provided to support and secure thereceiving container 73 to the unshaped members 78, 79 of the seat frame12. The container support structure 72 is shaped to support thereceiving container 73 about the lip 731, and includes mounting rods 75a, 75 b and 76 a, 76 b for being received within corresponding aperturesprovided in the unshaped members 78, 79. To further stabilize thereceiving container 73 versus the container support structure 72,notches 732 are provided on either side of the container 73 forreceiving the mounting rods 76 a, 76 b. To effect mounting of thecontainer support structure 72 to the chair frame 12, the containersupport structure 72 is manually bent so that the mounting rods becomealigned with the corresponding apertures, and then the mounting rods areinserted into the corresponding apertures. The receiving container 73can then be mounted upon the container support structure 72.

Each of the side structures 800 a, 800 b is coupled to the main supportstructure 700 by a cross brace 80. Each of the side structures 800 a,800 b includes a respective one of the upper seat rails 84 a, 84 b and arespective one of the lower seat rails 85 a, 85 b. Each of the upperseat rails 84 a, 84 b extend rearwardly from a respective one of theopposite sides of the tube structure 77. Each one of a pair of posts 83a, 83 b extends downwardly from proximate the front end of a respectiveone of the upper seat rails 84 a, 84 b. Each post 83 a, 83 b ispivotally coupled to a respective one of the front vertical member 91 a,91 b of the chair frame 12 by a respective bolt extending through arespective pair of aligned apertures, one of the respective pair ofaligned apertures being provided in a respective one of the posts 83 a,83 b and the other of the respective pair of aligned apertures beingprovided in a respective one of the members 91 a, 91 b. This effectspivotal coupling of the seat 14 to the chair frame 12.

Each of the upper seat rails 84 a, 84 b is pivotally coupled to one endof a respective one of a pair of extendible/retractable support members202 a, 202 b, at a point on the respective one of the upper seat rails84 a, 84 b disposed rearwardly of the point of pivotal coupling of theupper seat rail 84 a, 84 b to the backrest 18. The pivotal couplingbetween each one of the respective pair of aligned apertures beingprovided in a respective one of the rails 84 a, 84 b and a respectiveone of the members 202 a, 202 b is effected by a respective boltextending through a respective pair of aligned apertures, one of therespective pair of aligned apertures being provided in a respective oneof the rails 84 a, 84 b and the other of the respective pair of alignedapertures being provided in a respective one of the members 202 a, 202b. Each of the extendible/retractable support members 202 a, 202 b isalso pivotally coupled at an opposite end to the backrest 16. Thepivotal coupling between each of the members 202 a, 202 b and arespective one of a pair of opposing portions of the backrest 16 iseffected by a respective bolt extending through a respective pair ofaligned apertures, one of the respective pair of aligned apertures beingprovided in a respective one of the members 202 a, 202 b and the otherbeing provided in a respective one of an opposing pair of portions ofthe backrest 16. The members 202 a, 202 b enable positioning and supportof the backrest 16 in various positions of inclination relative to theseat 14, as is further described below.

Each of the lower seat rails 85 a, 85 b is coupled to and extendsrearwardly from a respective one of the posts 83 a, 83 b. Each of thelower seat rails 85 a, 85 b is coupled to a respective one of the pairof posts 81 a, 81 b at about a midpoint of the rail. Each of the posts81 a, 81 b, extends upwardly from a respective one of the rails 85 a, 85b and is pivotally coupled to a respective one of theextendible/retractable members 200 a, 200 b (see above). Each lower seatrail 85 a, 85 b also includes a respective one of two pairs of armrestsockets 86 a, 86 b and 87 a, 87 b.

Referring to FIGS. 6 and 7, an adjustable armrest assembly 500 for thebariatric chair 10 is illustrated according to an embodiment of thepresent invention. The armrest assembly 500 comprises an armrest 522 forsupporting a forearm of an individual when seated in the chair 10, and acoupling member 555 for coupling the armrest 522 to an armrest side (550a or 550 b) of the chair 10. The armrest 522 includes an upper surface5222 configured for supporting at least a portion of a forearm of aperson occupying the chair 10. The upper surface 5222 includes anuppermost surface portion 5224. The coupling member 555 facilitateslateral movement of the armrest 522 relative to the chair 10 between atleast three indexed armrest positions. The armrest assembly 500 alsoincludes a locking mechanism 900 configured for acting on the couplingmember 555 so as to effect locking of the armrest 522 in any one of theat least three indexed locked positions.

It is understood that, when the armrest 522 becomes locked in one of theat least three indexed locked positions, the armrest 522 may or may notbe completely stationary, and if not completely stationary, then thearmrest 522 may move (ie. travel) a minor distance owing to the factthat interacting components which effect locking of the armrest 522 inthe one of the at least three indexed locking positions are configuredwith some play between them.

It is also understood that the at least three indexed armrest positionsare distinguished from one another by the fact that the spatialdisposition of the armrest 522 when locked in any one of the at leastthree indexed positions is never identical to the spatial disposition ofthe armrest 522 when locked in any of the other of the at least threeindexed positions. However, it is also understood that the spatialdisposition of a first portion of the armrest, when the armrest 522 isdisposed in a first spatial position, may overlap (ie. occupy the samespace) with the spatial disposition of a second portion of the armrest522, when the armrest 522 is disposed in a second spatial position. Forexample, referring to FIGS. 8 and 10 which illustrate the armrest 522 inrespective forward narrow and rearward narrow positions, portion ‘A’ ofthe armrest 522 is shown moving laterally and rearwardly as the armrest522 moves from the forward narrow position (FIG. 8) to the wide rearwardnarrow position (FIG. 10). When the armrest 522 is in the forward narrowposition, portion ‘B’ of the armrest 522 is disposed in (occupies) acertain space, relative to the chair 10. When the armrest 522 is in therearward narrow position, portion ‘A’ of the armrest 522 is disposed inthis same space (ie. the space occupied by portion ‘B’ when the armrest522 is disposed in the forward narrow position). In this respect, thespatial disposition of portion ‘A’, when the armrest 522 is lateral in afirst position, overlaps with the spatial disposition of portion ‘B’when the armrest 522 is lateral in a second position.

With particular reference to the case where the armrest 522 is notcompletely stationary when locked in at least one of the at least threeindexed positions, it is also understood that the at least three indexedarmrest positions are distinguished from one another by the fact that,where there is some movement of the armrest 522 when in one of the atleast one of the at least three indexed positions, the various spatialdispositions of the armrest 522 within the scope of travel of thearmrest 522 in such indexed position are never identical to the spatialdisposition or dispositions (in the case where there is minor movementof the armrest 522 in another indexed position) of the armrest in any ofthe other of the at least three indexed positions (although a spatialdisposition of a portion of the armrest 522, when the armrest 522 isdisposed in a first spatial position, may overlap with a spatialdisposition of a second portion of the armrest 522, when the armrest 522is disposed in a second spatial position).

In the embodiment illustrated in FIG. 1, the chair 10 is configured withan armrest assembly 500 on each armrest side 550 a, 550 b of the chair10. FIGS. 6 and 7 illustrate an armrest assembly 500 of one side 500 aof the chair 10. The armrest assembly 500 for the opposite side 550 b ofthe chair 10 is a mirror image of the armrest assembly of the side 550 aof the chair 10.

The armrest assembly 550 can form an integral part of the chair 10.Alternately, the armrest assembly 550 may be configured for connectionto the chair. In the embodiment illustrated in FIG. 1, two armrestassemblies 500 are provided, and each is connected to a respective oneof the opposite armrest sides 550 a, 550 b of the chair 10.

The armrest 522 may include any padded armrest known to those skilled inthe art. For example, the armrest 522 may include a molded plasticmaterial. As a further example, the armrest 522 is constructed ofself-skinning polyurethane foam molded over a plywood inner cores andhas two internally embedded threaded steel inserts used for fastening.It will be apparent to those skilled in the art that any armrest thatcan support an arm of an individual when seated in the chair may beemployed.

In the illustrated embodiment, the coupling member 555, which permitslateral movement of the armrest member 522 relative to the chair 510, isa four-bar linkage assembly as is known to those skilled in the art. Thefour-bar linkage assembly comprises a stationary linkage 565, swivellinkages 570, 670, and an armrest coupling linkage 575.

The stationary linkage 565 is either configured for coupling to anarmrest side 500 a (or 500 b) of the chair 10, or is formed as anintegral part of the chair 10 and is disposed at an armrest side 500 a(or 500 b) of the chair 10. In the illustrated embodiment, thestationary linkage 565 is integral to the chair 10, and the stationarylinkage 575 forms a portion of each of the upper rails 84 a, 84 b (aseach side 500 a, 500 b includes an armrest assembly 500).

The swivel linkages 570 and 670 are provided to effect coupling of thearmrest coupling linkage 575 to the stationary linkage 565 whilefacilitating lateral movement of the armrest coupling linkage 575relative to the stationary linkage 565. Each of the swivel linkages 570,670 is rotatably connected to the stationary linkage 565 in spaced-apartrelationship to one another along a length of the stationary linkage 565such that the swivel linkage 570 is rotatably connected to thestationary linkage 565 closer to the front of the chair 10 and theswivel linkage 670 is rotatably connected to the stationary linkage 565closer to the back of the chair 10.

Each of the swivel linkages 570, 670 is also rotatably connected to thearmrest coupling linkage 575 in spaced apart relationship to one anotheralong a length of the armrest coupling linkage 575, such that the swivellinkage 570 is rotatably connected to the armrest coupling linkage 575closer to the front of the chair and the swivel linkage 670 is rotatablyconnected to the armrest coupling linkage 575 closer to the back of thechair 10. The connection of each of the swivel linkages 570, 670 to thearmrest coupling linkage 575 is offset relative to the respectiveconnection of each of the swivel linkages 570, 670 to the stationarylinkage 565.

The armrest coupling linkage 575 is connected to the armrest member 522,such as by screw 521.

The stationary linkage 565 includes an elongated frame member 510 havinga front joint portion 577 and a back joint portion 579, such that thefront joint portion 577 is positioned closer to the front of the chair10 and the back joint portion 579 is positioned closer to the back ofthe chair 10. Each of the joint portions 577, 579 preferably includes arespective one of offset posts 511 a, 511 b. Each of the posts 511 a,511 b extends laterally from the frame member 510 and includes arespective one of sockets 512 a, 512 b. Each of the sockets 512 a, 512 bis in the form of a tube segment defining a throughbore 5124 having asubstantially circular cross-section along its length between respectiveends of the tube segment. An axis passing through the throughbore 5124of each of the respective sockets 512 a, 512 b is oriented orthogonallyto the longitudinal axis of the respective offset post 511 a, 511 b(FIG. 7).

The swivel linkage 570 includes a stationary linkage joint portion 525and an armrest joint portion 516. The stationary linkage joint portion525 is offset from the armrest joint portion 516 and joined to thearmrest joint portion 516 by a laterally extending connector 517. Thestationary linkage portion 525 is rotatably connected to the socket 512a of the stationary linkage 565, thereby facilitating rotatable movementof the swivel linkage 570 about the axis passing through the socket 512a.

The stationary joint portion 525 includes upper and lower concentriccylindrical segments 5252, 5254. The diameter of the upper segment 5252is greater than the diameter of the lower segment 5254. The segment 5254is received within and rotatably engaged to the socket 512 a. The lowersegment 5254 is joined to the upper segment 5252 by a surface 5256extending peripherally and outwardly from the lower segment 5254. Thesurface 5256 is seated upon a shoulder portion 5122 of the socket 512(and thereby effecting vertical support of the surface 5256 by theshoulder portion 5122) when the tube segment 5252 is received within thesocket 512 a. In this respect, the stationary joint portion 525 isrotatably connected to the socket 512 a and is configured for rotationrelative to the socket 512 a about the axis 5251. In the illustratedembodiment, the axis 5251 is vertical.

A locking mechanism 701 is provided to prevent disengagement of thestationary joint portion 525 from the socket 512 a by limiting upwardsdisplacement of the stationary joint portion 525 relative to the socket512 a. When the locking mechanism 701 is in the operative condition, thestationary joint portion 525 is secured to the socket 512 a. When thelocking mechanism 701 is in an inoperative condition, the stationaryjoint portion 525 is unsecured relative to the socket 512 a. Thestationary joint portion 525 is secured to the socket 512 a by effectinginterference of upwards displacement of the stationary joint portion 525relative to the socket 512 a. Such interference action is accommodatedby having the stationary joint portion 525 extend through and below thesocket 512 a, and having a lower portion 5258 of the lower segment 5254of the stationary joint portion 525 extending below the socket 512 acoupled to a moveable detent 703 which selectively abuts against a lowerend of the socket 512 a if an attempt is made to pull the stationaryjoint portion 525 out of the socket 512 a.

In order for the stationary joint portion 525 to assume an unsecuredcondition relative to the socket 512 a, the detent 703 is configured soas to be capable of receding to a position which does not interfere withthe upwards displacement of the stationary joint portion 525 relative tothe socket 512 a. When the detent 703 is so receded, the lockingmechanism 701 is in the inoperative condition. When the detent 703 is inthe outwardly extended position, interfering with the upwardsdisplacement as described above, the locking mechanism 701 is in theoperative condition.

To facilitate the above-described operation of the locking mechanism701, the socket 512 a is open ended at both ends 530 a, 531 a and thethroughbore 5124 joins the ends 530 a, 531 a. This permits insertion ofthe stationary joint portion 525 into the socket 512 a such that thelower portion 5258 extends below the socket 512 a. Also, stationaryjoint portion 525 includes a bore 5260 which communicates externally ofthe stationary joint portion 525 through a hole 5262 provided in thesidewall of the lower portion 5258. The bore 5260 and the hole 5262accommodate the locking mechanism 701.

The locking mechanism 701 includes a detent pin spring 705 having firstand second portions 707, 709, and the detent pin 703 coupled to thespring 705 between the first and second portions 707, 709. The detentspring 705 is disposed within the bore 5260. When the locking mechanism701 is in the operative condition, the first and second portions 707,709 bear against a respective one of opposing inner surface portions ofthe stationary joint portion 525, and the detent pin 703 is positionedwithin and extends through the hole 5262 and outwardly relative to thelower portion 5258 (thereby providing a means for interfering withupwards displacement of the stationary joint end 525 relative to thesocket 512 a, as discussed above) by the biasing force exerted by thespring 705. When the locking mechanism 701 is in the inoperativecondition, the detent pin 703 is positioned in alignment with the hole5262 but disposed so as not to extend outwardly relative to the externalsurface of the lower portion 5258. In this position, the detent pin 703does not interfere with upwards displacement of the stationary jointportion 525 relative to the socket, and thereby permits the stationaryjoint end 525 to be pulled out of the socket 512. The detent pin 703 canbe moved to this position from its extended position outside of the hole5262 by applying a manual force on the pin 703 in a direction oppositeto, and overcoming the biasing force imparted by the spring 705.

The armrest joint portion 516 is rotatably connected to the armrestcoupling linkage 575 closer to the front of the chair 10 relative to theconnection of an armrest joint portion 616 of the swivel linkage 670 tothe armrest coupling linkage 575 (see below). The armrest joint portion516 preferably includes upper and lower concentric cylindrical segments5162, 5164. The diameter of the lower segment 5164 is greater than thediameter of the upper segment 5162. The segment 5162 is received withina bore 5753 of a cylindrical tubular segment 5752 of the armrestcoupling linkage 575, and thereby is rotatably engaged to the segment5752. The upper segment 5162 is joined to the lower segment 5164 by asurface 5166 extending peripherally and outwardly from the upper segment5162. The surface 5164 functions as a shoulder or seating surface uponwhich the segment 5752 of the linkage 575 is seated when the segment5162 is disposed within the segment 5752, thereby effecting verticalsupport of the segment 5752 by the surface 5164. The armrest jointportion 516 is configured for rotation relative to the segment 5752about an axis 5161. In the illustrated embodiment, the axis 5161 isvertical.

The swivel linkage 570 is, therefore, rotatably coupled to thestationary linkage 656 for rotation about the axis 5251, and is alsorotatably coupled to the armrest coupling linkage 575 for rotation aboutthe axis 5161. The distance between the axis 5251 and the axis 5161 (SeeFIG. 11), in the plane 5220 which is tangent to the uppermost surfaceportion 5224, is denoted by reference numeral 2.

The swivel linkage 670 includes a stationary linkage joint portion 625and an armrest joint portion 616. The stationary linkage joint portion625 is offset from the armrest joint portion 616 and joined to thearmrest joint portion 616 by a laterally extending connector 617. Thestationary linkage joint portion 625 is rotatably connected to thesocket 512 b of the stationary linkage 665, thereby facilitatingrotatable movement of the swivel linkage 670 about the axis passingthrough the socket 512 b.

The stationary joint portion 625 includes upper and lower concentriccylindrical segments 6252, 6254. The diameter of the upper segment 6252is greater than the diameter of the lower segment 6254. The segment 6254is received within and rotatably engaged to the socket 512 b. The lowersegment 6254 is joined to the upper segment 6252 by a surface 6256extending peripherally and outwardly from the lower segment 6254. Thesurface 6256 is seated upon a shoulder portion 6122 of the socket 512(and thereby effecting vertical support of the surface 6256 by theshoulder portion 6122) when the tube segment 6254 is received within thesocket 512 b. In this respect, the stationary joint portion 625 isrotatably connected to the socket 512 b and is configured for rotationrelative to the socket 512 b about an axis 6251. In the illustratedembodiment, the axis 6251 is vertical.

A locking mechanism 801 is provided to prevent disengagement of thestationary joint portion 625 from the socket 512 b by limiting upwardsdisplacement of the stationary joint portion 625 relative to the socket512 b. When the locking mechanism 801 is in the operative condition, thestationary joint portion 625 is secured to the socket 512 b. When thelocking mechanism 801 is in an inoperative condition, the stationaryjoint portion 625 is unsecured relative to the socket 512 b. Thestationary joint portion 625 is secured to the socket 512 b by effectinginterference of upwards displacement of the stationary joint portion 625relative to the socket 512 b. Such interference is accommodated byhaving the stationary joint portion 625 extend through and below thesocket 512 b, and having a lower portion 6258 of the lower segment 6254of the stationary joint portion 625 extending below the socket 512 bcoupled to a moveable detent 803 which is configured to abut against alower end of the socket 512 b if an attempt is made to pull thestationary joint portion 625 out of the socket 512 b.

In order for the stationary joint portion 625 to assume an unsecuredcondition relative to the socket 512 b, the detent 803 is configured soas to be capable of receding to a position which does not interfere withthe upwards displacement of the stationary joint portion 625 relative tothe socket 512 b. When the detent 803 is so receded, the lockingmechanism 801 is in the inoperative condition. When the detent 803 is inthe outwardly extended position, interfering with the upwardsdisplacement as described above, the locking mechanism 801 is in theoperative condition.

To facilitate the above-described operation of the locking mechanism801, the socket 512 b is open ended at both ends 630 a, 631 a and thethroughbore 6124 joins the ends 630 a, 631 a. This permits insertion ofthe stationary joint portion 625 into the socket 512 b such that thelower portion 6258 extends below the socket 512 b. Also, stationaryjoint portion 6525 includes a bore 6260 which communicates externally ofthe stationary joint portion 625 through a hole 6262 provided in thesidewall of the lower portion 6258. The bore 6260 and the hole 6262accommodate the locking mechanism 801.

The locking mechanism 801 includes a detent pin spring 805 having firstand second portions 807, 809, and the detent pin 803 coupled to thespring 805 between the first and second portions 807, 809. The detentspring 805 is disposed within the bore 6260. When the locking mechanismis in the operative condition, the first and second portions 807, 809bear against a respective one of opposing inner surface portions of thestationary joint portion 625, and the detent pin 803 is positionedwithin and extends through the hole 6262 and outwardly relative to thelower portion 6258 (thereby providing a means for interfering withupwards displacement of the stationary joint end 525 relative to thesocket 512 a, as discussed above) by the biasing force exerted by thespring 805. When the locking mechanism 801 is in the inoperativecondition, the detent pin 803 is positioned in alignment with the hole6262 but disposed so as not to extend outwardly relative to the externalsurface of the lower portion 6258. In this position, the detent pin 803does not interfere with upwards displacement of the stationary jointportion 625 relative to the socket, and thereby permits the stationaryjoint end 625 to be pulled out of the socket 512. The detent pin 803 canbe moved to this position from its extended position outside of the hole6262 by applying a manual force on the pin 803 in a direction oppositeto, and overcoming the biasing force imparted by the spring 805.

The armrest joint portion 616 is rotatably connected to the armrestcoupling linkage 575 closer to the back of the chair 10 relative to theconnection of an armrest joint portion 516 of the swivel linkage 570 tothe armrest coupling linkage 575. The armrest joint portion 616preferably includes upper and lower concentric cylindrical segments6162, 6164. The diameter of the lower segment 6164 is greater than thediameter of the upper segment 6162. The segment 6162 is received withina bore 6753 of a cylindrical, tubular segment 6752 of the armrestcoupling linkage 575, and thereby is rotatably engaged to the segment6752. The upper segment 6162 is joined to the lower segment 6164 by asurface 6166 extending peripherally and outwardly from the upper segment6162. The surface 6164 functions as a shoulder or seating surface uponwhich the segment 6752 of the linkage 575 is seated when the segment6162 is disposed within the segment 6752, thereby effecting verticalsupport of the segment 6752 by the surface 6166. The armrest jointportion 616 is configured for rotation relative to the segment 6752about an axis 6161. In the illustrated embodiment, the axis 6161 isvertical.

The swivel linkage 670 is, therefore, rotatably coupled to thestationary linkage 565 for rotation about the axis 6251, and is alsorotatably coupled to the armrest coupling linkage about the axis 6161.The distance between the axis 6251 and the axis 6161 (see FIG. 12), inthe plane 5220 (which is tangent to the uppermost surface portion 5224),is denoted by reference numeral 4.

In one embodiment, the distance 2 is the same or substantially the sameas the distance 4. In another embodiment, the distance 2 is at least 1.2times longer than the distance 4 (ie. the ratio of the distance 2 to thedistance 4 is 1.2). For example, the distance 2 is at least 1.5 timeslonger than the distance 4. As a further, further example, the distanceis at least two (2) times longer than the distance 4. By having thedistance 2 being longer than the distance 4, additional space isprovided between the armrest assemblies 500 a, 500 b closer to the frontof the chair than closer to the rear of the chair 10. Typically, abariatric patient seated in the chair 10 requires additional room forcomfort closer to the front of the chair, and this is accommodated byhaving the distance 2 being longer than the distance 4.

The armrest coupling linkage 575 includes a front joint portion 589 fromwhich the segment 5752 extends downwardly, and a back joint portion 591,from which the segment 6752 extends downwardly. The armrest linkage 575is rotatably connected to each of (i) the armrest joint portion 516 oflinkage 570, and (ii) the armrest joint portion 616 of the linkage 670,by a respective one of the segments 5752, 6752, thereby permittingrotatable movement of the swivel linkages 570, 670 about the respectiveaxes 5161, 6161 and lateral movement of the armrest coupling linkage 575relative to the stationary linkage 565 (and also, therefore, relative tothe chair 10).

The front and back joint portions 589, 591 are joined by an elongatedframe member 520. The armrest member 522 is suitably connected to theelongated member 520 so as to present a surface upon which a personseated in the chair can rest his or her arms on the armrest member 522for support. In the illustrated embodiment, the armrest member 522 isconnected to the frame member 520 by screws 521 a, 521 b.

A locking mechanism 900 is provided to selectively limit relativerotational movement between the swivel linkage 570 and the armrestcoupling linkage 575 and between the swivel linkage 670 and the armrestcoupling linkage 575, when the armrest is in any one of a first narrowarmrest position, an intermediate wide armrest position, or a secondnarrow armrest position. An example of the above-described relativerotational movement being limited by the locking mechanism 900 is whenthe above-described relative rotational movement is substantiallyprevented by the locking mechanism 900. In this context, the term“substantially prevented” means that the above-described relativerotational movement may or may not be prevented, and if not prevented,the above-described relative rotational movement is limited such thatthe relative rotational movement between the linkages 570, 670 and thelinkage 575 is minor and not sufficiently significant so as tonoticeably derogate from the chair occupant's expectations that his orher arm is maintained in a stationary position when supported on thearmrest 552.

The locking mechanism 900 includes at least a first locking element 902.The first locking element 902 is configured to act between the swivellinkage 570 and the armrest coupling linkage 575 to oppose tangentialforces relative to swivel linkages 560, 670, being applied by thearmrest coupling linkage 575 that would otherwise effect swivelling ofthe linkages 560, 570. This limits (for example, substantially prevents)the above-described rotational movement of the linkages 560, 670relative to the linkage 575 and thereby maintain the armrest 522 in anyone of the three above-described positions. In the illustratedembodiment, the locking mechanism 900 includes a second locking element952. The second locking element 952 is configured to act between theswivel linkage 670 and the armrest coupling linkage 575 to opposetangential forces relative to swivel linkages 560, 670, being applied byarmrest coupling linkage 575 that would otherwise effect swivelling ofthe linkages 560, 670. This assists locking element 902 by distributingloading between two locking elements instead of only one locking elementin limiting (for example, substantially preventing) the above-describedrelative rotational movements.

The locking mechanism 900 is in the operative condition when relativerotational movement between the swivel linkage 570 and the armrestcoupling linkage 575, and between the swivel linkage 670 and the armrestcoupling linkage 575, is limited (for example, substantially prevented).The locking mechanism 900 is in the operative condition when at leastone of the locking elements 902, 952 is acting between the armrestcoupling linkage 575 and a respective one of the swivel linkages 570,670. When both of the locking elements 902, 952 are acting in thismanner, each locking element 902, 952 is individually described as beingin an operative condition.

The locking mechanism 900 is in the inoperative condition when each ofthe swivel linkages 570, 670 is free to rotate relative to the armrestcoupling linkage 575, subject to any interference to the rotationalmovement provided by other components of the assembly 500 or the chair10 (such as stationary linkage 565). The locking mechanism 900 is in theinoperative condition when the locking element 902 is not acting betweenthe armrest coupling linkage 575 and the swivel linkage 570 (in whichcase, locking element 902 can also be described as being in an“inoperative condition”), and the locking element 952 is not actingbetween the armrest coupling linkage 575 and the swivel linkage 670 (inwhich case, locking element 952 can also be described as being in an“inoperative condition”). In other words, for the locking mechanism 900to be in the inoperative condition, each of the locking elements 902,952 must also be in the inoperative condition.

The locking element 902 acts between the swivel linkage 570 and thearmrest coupling linkage 575 by effecting interference of relativerotational movement between the swivel linkage 570 and the armrestcoupling linkage 575 (as well as linkages 670 and 575). The lockingelement 902 is coupled to the swivel linkage 570 and includes a moveabledetent pin 904. The detent pin 904 is configured to be received withinand extend through an armrest linkage hole 528 provided in the sidewallof the segment 5752 of the armrest coupling linkage 575. In other words,the detent pin 904 is configured to interfere with the relativerotational movement between the swivel linkage 570 and the armrestcoupling linkage 575. In this respect, when the detent pin 904 extendsthrough the armrest linkage hole 528, and an attempt is made to effectrelative rotation between the swivel linkage 560 and the armrestcoupling linkage 575, the detent pin 904 becomes abutted against aninner edge surface of the armrest coupling linkage 575 which defines thehole 528, thereby limiting relative rotational movement between theswivel linkage 570 and the armrest coupling linkage 575.

In order for the swivel linkage 570 to assume an unsecured conditionrelative to the armrest coupling linkage 575, the detent pin 904 isconfigured to be capable of receding to a position which does notinterfere with the relative rotational movement between the swivellinkage 570 and the armrest coupling linkage 575. When the detent pin904 is so receded, the locking element 902 in the inoperative condition.When the detent pin 904 is in an outwardly extended position, extendingthrough the hole 528, and thereby interfering with the above-describedrelative rotational movement, the locking element 902 is in theoperative condition.

To accommodate the locking element 902, the armrest joint portion 516 ofthe swivel linkage 570 includes a bore 5601 which communicatesexternally of the armrest joint portion 516 through a swivel linkagehole 523 provided in the sidewall of the upper segment 5162.

The locking element 902 includes a detent spring 906 having first andsecond portions 908, 910. The detent pin 904 is coupled to the spring906 between the first and second portions 908, 910. The detent spring906 is disposed within the bore 5601 and the first and second portions908, 910 bear against a respective one of opposing inner surfaceportions of the armrest joint portion 516.

When the locking element 902 is in the operative condition, both of thearmrest linkage hole 528 and the swivel linkage hole 523 are aligned,the first and second portions 908, 910 bear against a respective one ofopposing inner surface portions of the armrest joint portion 516, andthe detent pin 904 is positioned within and extends through each of theswivel linkage hole 523 and the armrest linkage hole 528 by the biasingforce exerted by the spring 906.

When the locking element 902 is in the inoperative condition, the detentpin 904 extends through the swivel linkage hole 523 but does not extendinto the armrest linkage hole 528 and, therefore, does not interferewith relative rotational movement between the swivel linkage 560 and thearmrest coupling linkage 575. The detent pin 904 can be moved to thisreceded position from its extended position through the hole 528 byapplying a manual force on the pin 904 in a direction opposite to, andovercoming the biasing force imparted by the spring 906.

Once the pin 904 is moved into and maintained in this receded position,the swivel linkage 560 and the armrest coupling linkage 575 can bemeaningfully rotated relative to one another, thereby taking the holes523 and 528 out of alignment. As a result, the detent pin 904 is biasedinto a position wherein the detent pin 904 extends through the swivellinkage hole 526 and is in sliding contact with the inner surface of thebore 5753 of the segment 5752. However, such contact does not interferewith relative rotational movement between the swivel linkage 560 and thearmrest coupling linkage 575 so long as the friction created by spring906, between detent pin 904 and the inner surface of the bore 5753 issignificantly less than the rotational force acting at that interface.For example, this would be the case where the bore 5753 has a circularor substantially circular cross-section along its length which receivesthe segment 5162.

The segment 5752 includes a plurality of holes 528 about its perimeter,wherein each of the plurality of holes corresponds to a desired indexedposition of the armrest 522. In the illustrated embodiment, the segment5752 includes three (3) holes 528, wherein each of the holes 528corresponds to a respective one of a first narrow armrest position, anintermediate wide armrest position, and a second narrow armrestposition. The armrest 522 is disposed in one of these positions wheneverthe detent pin 904 extends through a respective one of the holes 528.The armrest 522 moves between these positions as the armrest couplinglinkage 575 rotates relative to the swivel linkage 560 from a positionof alignment of one of the holes 528 with the hole 523 of the swivellinkage 560 (ie. a first operative condition of the locking element 902)to a position of alignment of another one of the holes 528 with the hole523 (ie. a second operative condition of the locking element 902).

The locking element 952 acts between the swivel linkage 670 and thearmrest coupling linkage 575 by effecting interference of relativerotational movement between the swivel linkage 670 and the armrestcoupling linkage 575. The locking element 952 is coupled to the swivellinkage 670 and includes a moveable detent pin 954. The detent pin 954is configured to be received within and extend through an armrestlinkage hole 628 provided in the sidewall of the segment 6752 of thearmrest coupling linkage 575. In other words, the detent pin 954 isconfigured to interfere with the relative rotational movement betweenthe swivel linkage 670 and the armrest coupling linkage 575. In thisrespect, when the detent pin 954 extends through the armrest linkagehole 628, and an attempt is made to effect relative rotation between theswivel linkage 570 and the armrest coupling linkage 575, the detent pin954 becomes abutted against an inner edge surface of the armrestcoupling linkage 575 which defines the hole 628, thereby limitingrelative rotational movement between the swivel linkage 670 and thearmrest coupling linkage 575.

In order for the swivel linkage 670 to assume an unsecured conditionrelative to the armrest coupling linkage 575, the detent pin 954 isconfigured to be capable of receding to a position which does notinterfere with the relative rotational movement between the swivellinkage 670 and the armrest coupling linkage 575. When the detent pin954 is so receded, the locking element 952 is in the inoperativecondition. When the detent pin 954 is in an outwardly extended position,extending through the hole 628, and thereby interfering with theabove-described relative rotational movement, the locking element 952 isin the operative condition.

To accommodate the locking element 952, the armrest joint portion 616 ofthe swivel linkage 670 includes a bore 6601 which communicatesexternally of the armrest joint portion 616 through a swivel linkagehole 623 provided in the upper segment 6162.

The locking element 952 includes a detent spring 956 having first- andsecond portions 958, 960. A detent pin 956 is coupled to the spring 956between the first and second portions 958, 960. The detent spring 956 isdisposed within the bore 6601 and the first and second portions 908, 910bear against a respective one of opposing inner surface portions of thearmrest joint portion 616.

When the locking element 660 is in the operative condition, both of thearmrest linkage hole 628 and the swivel linkage hole 623 are aligned,the first and second portions 958, 960 bear against a respective one ofopposing inner surface portions of the armrest joint portion 516, andthe detent pin 954 is positioned within and extends through each of theswivel linkage hole 623 and the armrest linkage hole 628 by the biasingforce exerted by the spring 956.

When the locking element 954 is in the inoperative condition, the detentpin 954 extends through the swivel linkage hole 623 but does not extendinto the armrest linkage hole 628 and, therefore, does not interferewith relative rotational movement between the swivel linkage 670 and thearmrest coupling linkage 575. The detent pin 954 can be moved to thisreceded position from its extended position through the hole 628 byapplying a manual force on the pin 954 in a direction opposite to, andovercoming the biasing force imparted by the spring 956.

Once the pin 954 is moved into and maintained in this receded position,the swivel linkage 670 and the armrest coupling linkage 575 can berotated relative to one another, thereby taking the holes 623 and 628out of alignment. As a result, the detent pin 954 is biased into aposition wherein the detent pin 954 extends through the swivel linkagehole 628 and is in sliding contact with the inner surface of the bore6753 of the segment 6752. However, such contact does not interfere withrelative rotational movement between the swivel linkage 670 and thearmrest coupling linkage 575 so long as the friction created by thespring 906 between detent pin 904 and the inner surface of the bore 6753is significantly less than the rotational force acting at thatinterface. For example, this would be the case where the bore 6753 has acircular or substantially circular cross-section along its length whichreceives segment 6162.

The segment 6752 includes a plurality of holes 628 about its perimeter,wherein each of the plurality of holes corresponds to a desired indexedposition of the armrest 522. In the illustrated embodiment, the segment6752 includes three (3) holes 628, wherein each of the holes 628corresponds to a respective one of a forward narrow armrest position, anintermediate wide armrest position, and a rear narrow armrest position.The armrest 522 is disposed in one of these positions whenever thedetent pin 954 extends through a respective one of the holes 628. Thearmrest 522 moves between these positions as the armrest couplinglinkage 575 rotates relative to the swivel linkage 670 from a positionof alignment of one of the holes 628 with the hole 623 of the swivellinkage 670 (ie. a first operative condition of the locking element 952)to a position of alignment of another one of the holes 628 with the hole623 (ie. a second operative condition of the locking element 952).

The armrest assembly 500 is moveable between at least three indexedpositions. In the embodiment illustrated in FIGS. 1, 8, 9 and 10, thearmrest assembly 500 is moveable between three indexed positions,namely: a forward narrow position (FIG. 8), in which the armrest 522 isin a narrow position at about the front end of the chair 10, a mid-wideposition (FIG. 9), in which the armrest 522 is in a wide position atabout the mid-point of the chair 10, and a rear narrow position (FIG.10), in which the armrest 522 is in a narrow position at about the backof the chair 10. As the assembly 500 moves to each of these positions,the armrest 522 follows an arc-like path, which is generally indicatedby the arrow in each of FIGS. 8, 9 and 10. This arc-like path, resultsin lateral movement of the armrest 522 relative to the chair 10, betweena forward narrow position, an intermediate wide position, and a rearwardnarrow position. For example, the lateral distance moved between eitherof the narrow positions and the wide position is no greater than three(3) inches. As a further example, this lateral distance moved is two (2)inches.

In an alternate embodiment, the coupling member 555 comprises a singleswivel linkage of a configuration identical to that of either swivellinkage 570 or 670, and would be rotatably connected to the stationarylinkage 565 in an identical manner to that described for the coupling ofeither of the swivel linkages 570, 670 to a respective one of thesockets 12 a, 12 b of the stationary linkage 565. The single swivellinkage would be further rotatably connected to the armrest couplinglinkage 575 in an identical manner to that described for the coupling ofeither of the swivel linkages 570, 670 to the respective one of thesegments 5752, 6752 of the armrest coupling linkage 575. For example,the single swivel linkage would be connected to the armrest couplinglinkage 575 at about a midpoint of the armrest coupling linkage 575 (asopposed to one of the end portions 589, 591) so as to realize a morestable structure. The locking mechanism 900 associated with the singleswivel linkage would be a single locking element 902 or 954, and wouldbe configured to limit (for example, substantially prevent) relativerotational movement between the single swivel linkage and the armrestcoupling linkage 575. Also, a single locking mechanism of theconfiguration described and illustrated for either locking mechanism 701or 801 could also be provided for preventing disengagement of thestationary joint portion of the single swivel linkage from an associatedsocket of the linkage 575.

In another embodiment the armrest assembly 500 includes more than twoswivel linkages to effect coupling of the linkage 575 to the linkage565.

Movement of the illustrated embodiment of the armrest 522 between theforward narrow position, the wide position, and the rearward narrowposition will now be described. Initially, the armrest 522 is in theforward narrow position (see FIG. 8), and each of the locking elements902, 952 is in the operative condition. As a first step, each of thedetent pins 904, 954 is manually depressed so that they recede into eachof their corresponding respective holes 528, 628, such that the detentpins 904, 954 are in a position wherein they cannot interfere with arespective one of relative rotational movement between linkage 570 andlinkage 575 and relative rotational movement between linkage 670 andlinkage 575 (ie. the locking elements 902, 952 are in the inoperativecondition). A manual force is then applied to the intermediate armrest522 to effect movement of the armrest 522 in an arc-like path from theforward narrow position to the wide position (see FIG. 9). As thearmrest 522 moves in this manner, each of the linkages 570, 670 rotatesrelative to the linkages 575, and each of the detent pins 904, 954 movesout of alignment with a respective one of a first set of holes 528, 628.When the armrest 522 assumes the intermediate wide position, each of thedetent pins 904, 954 is biased to extend through a respective one of thesecond set of holes 528, 568 so that each of the locking elements 902,952 assumes a second operative position, thereby locking the armrest 522in the intermediate wide position. To move the armrest 522 from theintermediate wide position to the rearward position (see FIG. 10), thedetent pins 904, 954 are, again, manually depressed so that they recedeinto each of their corresponding respective holes 528, 628, such thatthe detent pins 904, 954 are in a position whereby they cannot interferewith a respective one of relative rotational movement between linkage570 and linkage 575 and relative rotational movement between linkage 670and linkage 575 (ie. the locking elements 902, 952 are in theinoperative condition) A manual force is then applied to the armrest toeffect movement of the armrest in an arc-like path from the intermediatewide position to the rearward position (See FIG. 10). As the armrest 522moves in this manner, each of the linkages 570, 670 rotates relative tothe linkage 575, and each of the detent pins 904, 954 moves out ofalignment with a respective one of the second set of holes 528, 628.When the armrest 522 assumes the rearward narrow position, each of thedetent pins 904, 954 assumes alignment with a respective one of a thirdset of holes 528, 628, and the detent pins are biased to extend througha respective one of the third set of holes 528, 628, so that each of thelocking elements 902, 952 assumes a third operative position, therebylocking the armrest 522 in the rearward position.

Referring to FIGS. 6, 7, 11 and 12, the locking mechanism 900 mayfurther include a threaded handwheel to act between at least one of: (i)the linkage 560 and the linkage 575, and (ii) the linkage 670 and thelinkage 575, and thereby provide a further means for effectinginterference of relative rotational movement between both sets oflinkages (linkages 560, 575 and linkages 570, 575). In the illustratedembodiment, two threaded handwheels 1001, 1101 are provided. Thehandwheel 1001 acts between the linkage 560 and the linkage 575. Thehandwheel 1101 acts between the linkage 670 and the linkage 575.

The handwheel 1001 includes a threaded rod 1003 that threadably engagesa projection nut 1005 coupled to the segment 5752 of the linkage 575.The nut 1005 defines a bore 1007 which is co-axial with an openingprovided in the segment 5752 of the armrest coupling linkage 575. Theopening is a circular hole that has a diameter which is large enough toaccept the major diameter of the threaded rod 1003. The handwheel 1001can be turned so as to extend through the opening and bear against theupper segment 5162 of the armrest joint portion 516 of the swivellinkage 560, thereby interfering with relative rotational movementbetween the linkages 560 and 575 (as well as linkages 570 and 575). Thesecond handwheel 1101 is configured to bear against linkage 570 in asimilar manner. The handwheel 1101 includes a threaded rod 1103 thatthreadably engages a projection nut 1105 coupled to the segment 6752 ofthe linkage 575. The nut 1105 defines a bore 1107 which is co-axial withan opening provided in the segment 6752. The opening is a circular holdthat has a diameter which is large enough to accept the major diameterof the threaded rod 1003. The handwheel can be turned so as to extendthrough the opening and bear against the upper segment 6162 of thearmrest joint portion 616 of the swivel linkage 670, thereby interferingwith relative rotational movement between the linkages 670 and 575 (aswell as linkages 560 and 575).

Each of the handwheels 1001, 1101 is capable of limiting relativemovement between both sets of linkages when the armrest 522 is notdisposed in one of the three indexed positions (ie. the armrest 522 isdisposed in a non-indexed position), which is the case when holes 523and 528 are out of alignment (or when holes 623 and 628 are out ofalignment).

Accordingly, when the detent pins 904, 954 and the handwheel 1001 are intheir respective disengaged positions, the armrest linkage 575 may bemoved to a desired lateral position (FIG. 12). If this position does notcorrespond to an indexed position, then the handwheel 1003 may beengaged to thereby lock the sets of linkages and prevent further lateralmovement of the armrest linkage 575 (FIG. 11).

As discussed above, the seat 14 can be pivotally coupled to the chairframe 12. Pivotal coupling of the seat 14 to the chair frame 12facilitates pivotal movement of the combination of the seat 14 and thebackrest 16 (where the backrest 16 is coupled to the seat 14, as is thecase in the preferred embodiment, and as will be discussed below)relative to the chair frame 12. In this respect, the seat 14 is capableof moving from one position of seat tilt relative to the frame 12 toanother position of seat tilt (ie. changing the desired degree of seattilt).

Positioning and support of the seat 14 in various positions of tilt isenabled by the extendible/retractable support members 200 a, 200 b. Thesupport provided by the extendible/retractable support members 200 a,200 b is adjustable, in that the support members 200 a, 200 b can belocked in a first position, and then released to permit extension orretraction of the support member so that the desired degree of seat tiltcan be changed, and then locked again once the seat 14 is positioned atthe desired degree of seat tilt. This facilitates changing of thedesired degree of seat tilt, while effecting support of the seat 14,upon the seat 14 being positioned to the desired degree of seat tilt. Toaccommodate this change of positioning, and as explained above, each ofthe extendible/retractable members 200 a, 200 b is pivotally coupled atone end to the chair frame 12 (ie. braces 98 a, 98 b) and at a secondopposite end to the seat 14 (ie. posts 81 a, 81 b on the seat frame 18).Extendible/retractable members 200 a, 200 b are actuated for movement byhand actuators 201 a, 201 b.

Each of the extendible/retractable support members 200 a, 200 b is inthe form of a gas cylinder or “spring” provided on the chair frame 12 toexert an upward force on the seat 14 to thereby resist a downward weightof a chair occupant. A suitable gas spring is a BLOC-O-LIFT locking gasspring using a Bowden cable system, as manufactured by Stabilus GmbH. Adetailed drawing of an example of the extendible/retractable supportmembers 200 a, 200 b is provided in FIG. 17.

The gas spring is a closed system consisting of a pressure tube 102 anda hollow piston rod 104 extending from the pressure tube 102. The pistonrod 104 terminates in a piston within pressure tube 102. A compressedgas is provided within tube 102. The pressure tube 102 is separated intofirst and second chambers by a valve (not shown). The valve is actuatedby a release pin which extends from the valve and through the piston rod104, and extends externally of the piston rod 104 for actuation byrelease plate 106. When the valve is open, in response to depression ofthe release pin, the piston rod can be extended in a controlled,dampened manner at the defined gas spring force to the maximumextension, so long as the gas spring force exceeds any external opposingforces. Of course, supplementary external forces (such as a manualforce) can be applied to supplement the gas spring force and assist inthe extension of the members 200 a, 200 b. This results in extension ofthe extendible/retractable support members 200 a, 200 b. If, while thevalve is open, an external force is applied to the piston rod inopposition to the gas spring force, and overcoming the gas spring force,the piston rod 104 will recede into the pressure tube, resulting in theshortening of the length (ie. retraction) of the members 200 a, 200 b.An example of how such an external force may be applied to effectretraction of the members 200 a, 200 b is application of a manual forceto cross-member 40 of the backrest frame 34 in a generally downwardsdirection. As soon as the actuator pin is released from the outside, thevalve will close automatically because of the gas pressure exerted onit. The piston or piston rod is then locked, as gas exchange between thechambers is interrupted. The cylinders may thus be releasably locked ina desired position upon the seat 14 becoming titled to a desiredposition. The valve is manually controlled by tensioning of a cable(such as a Bowden™ cable) connected to the release plate 106 in responseto actuation of the hand actuator 107 (in the case of members 200 a, 200b, this would be actuators 201 a, 201 b respectively).

Alternatively, such extendible support members can be lockable helicalsprings or a ratchet mechanism.

The seat 14 is coupled to the chair frame 12 such that the verticaldistance accommodates a suitable floor to knee height for bariatricpatients using the chair. For example, the seating surface 20 of theseat 14 at the front edge 24 of the seat 14 is disposed above thereaction surface 8 (see FIG. 2) by a vertical distance of 21 inches. Asa further example, the vertical distance is 23 inches.

Referring to FIGS. 1, 2, 13 and 14, the backrest 16 includes a backrestframe 30 and a backrest front surface 32. In the illustrated embodiment,the backrest frame 30 is coupled to the seat frame 18. It is understoodthat it is not necessary to couple the backrest frame 30 to the seatframe 18, and that coupling between the backrest frame 30 and the chairframe 12 may be effected directly with the chair frame 12 independentlyof the seat frame 18. However, where it is desired to facilitate pivotalmovement between (i) the combination of the seat 14 and the backrest 16,and (ii) the chair frame 12 (ie. tilting of the seat 14) as it is in thepreferred embodiment, the backrest frame 30 is coupled, and moreparticularly, pivotally coupled to the seat frame 18.

The backrest frame 30 is pivotally coupled to the seat frame 18 at eachof the upper seat rails 84 a, 84 b, so as to facilitate pivotal movement(ie. movement into various positions of inclination) of the backrest 16relative to the seat 14 and the chairframe 12. In order to facilitatepivotal movement of the seat 14 and backrest 16 (ie. movement intovarious positions of seat tilt) relative to the chair frame 12, thebackrest frame 30 is pivotally coupled to the seat frame 18. Pivotalcoupling of the backrest frame 30 to the seat frame 18 enables movementof the backrest from one position of inclination (or “recline”) relativeto the seat 14 and the chair frame 12 to another position of inclination(ie. changing the desired degree of backrest inclination).

The backrest frame 30 is formed of two unitary spaced apart sidestructures 34 a, 34 b comprising a plurality of elongated bar or tubemembers. For example, the tube members are 304 stainless steel, one inchdiameter, 16 gauge (0.065 inch wall thickness) tubes.

Each of the unitary side structures 34 a, 34 b includes a respective oneof main tube members 36 a, 36 b. Each of the main tube members 36 a, 36b is pivotally coupled proximate the bottom end thereof to a respectiveone of the upper seat rails 84 a, 84 b of the seat frame 14, at aposition forwardly disposed of the rear end of a respective one of theupper seat rails 84 a, 84 b. The pivotal coupling between each one ofthe members 36 a, 36 b and a respective one of the rails 84 a, 84 b iseffected by a respective bolt extending through a respective pair ofaligned apertures, one of the respective pair of aligned apertures beingprovided in a respective one of the rails 84 a, 84 b and the other ofthe respective pair of aligned apertures being provided in a respectiveone of the members 36 a, 36 b. This effects pivotal coupling of thebackrest 16 to the seat 14.

Each of the members 36 a, 36 b extends upwardly from the seat frame 14.Each of the main tube members 36 a, 36 b is contoured to facilitate thedesired shaping of the backrest support surface 32, as is furtherdescribed below. The main tube members 36 a, 36 b are joined together ator proximate their respective upper ends by a substantially horizontaltop member 38 extending between the main tube members 36 a, 36 b. Asubstantially horizontal cross member 40 is also provided and extendsbetween the main tube members 36 a, 36 b and below the top member 38.The cross member 40 is pivotally coupled to one end of each of theextendible/retractable members 202 a, 202 b (see FIG. 4). This effectspivotal coupling of the extendible/retractable support members 202 a,202 b to the backrest 16. As well, hand levers associated with operationof the extendible/retractable members 202 a, 202 b, are also mounted tothe cross member 40. The cross member 40 also can be used as astroller-style push handle for a caregiver to propel the chair 10. Thecross member 40 is supported by a pair of spaced apart cross bracemembers 42 a, 42 b extending from the top member 38, and is alsosupported by a pair of reinforcing tubes 44 a, 44 b, where each of thereinforcing tubes 44 a, 44 b is coupled to and extends upwardly from arespective one of the main tube members 36 a, 36 b.

Positioning of the backrest 16 in various positions of inclinationrelative to the seat 14 is enabled by the extendable/retractable supportmembers 202 a, 202 b. The support provided by the extendible/retractablesupport members 202 a, 202 b is adjustable, in that the support members202 a, 202 b can be locked in a first position, and then released topermit extension or retraction of the support members 202 a, 202 b sothat the desired degree of backrest inclination can be changed, and thenlocked again once the backrest 16 is positioned at the desired degree ofinclination. This facilitates changing of the desired degree of backrestinclination, while enabling support of the backrest 16 upon the backrest16 being positioned to the desired degree of inclination.

In this respect, the extendible/retractable support members 202 a, 202 bare in the form of a pair of gas springs is provided on the chair frameto exert an upward force on the backrest to thereby resist a downwardweight of a chair occupant. A suitable gas spring is a BLOC-O-LIFTlocking gas spring using a Bowden cable system, as manufactured byStabilus GmbH. A detailed drawing of an embodiment of theextendible/retractable support members 202 a, 202 b is provided in FIG.17. The general operation of the extendible/retractable support members202 a, 202 b is the same as that described above forextendible/retractable support members 200 a, 200 b, with the exceptionthat actuation of the members 202 a, 202 b is effected by hand actuators203 a, 203 b, respectively.

The backrest front surface 32 is configured for receiving and supportingat least a portion of the upper torso of the chair occupant. Like theseating surface 20, the front surface 32 of the backrest 16 can be acontinuous or a discontinuous surface, so long as the front surface 32performs the function of providing the necessary support to the chairoccupant. In the illustrated embodiment, the backrest front surface 32includes a plurality of spaced apart vinyl straps coupled to each of andextending between the tube members 36 a, 36 b. An exemplary vinyl strapis an extruded vinyl strap (1.5 inches wide, 0.13 inches thick, with aconvex radius along its width) manufactured by Twitchell Corporation.

The backrest front surface 32 includes an upper backrest front surface46 and a lower backrest front surface 48. The lower backrest frontsurface 48 is recessed relative to the upper backrest front surface 46in order to accommodate the lower torso of a bariatric patient who isoccupying the chair 10. The space 52 within the recess is configured soas to accommodate and receive soft tissue in the gluteal region (ie. a“gluteal shelf”) of the chair occupant where such soft tissue has becomedisplaced rearwardly as a result of the chair occupant being seated inthe chair. The desirability of accommodating a gluteal shelf ispronounced with bariatric patients, where the presence of a glutealshelf is particularly significant when a bariatric patient is disposedin a seating position. Without providing any space in a chair foraccommodating the gluteal shelf, seating of a bariatric patient in achair can be relatively uncomfortable.

In this respect, the backrest 16 includes a backrest front supportsurface 32 including an upper backrest front surface 46 and a lowerbackrest front surface 48, the lower backrest front surface 48 beingrecessed from, and merging with the upper backrest front surface 46 at amerged front surface 50. An upper backrest front merging surface 4602extends upwardly from the merged front surface 50, and a lower backrestfront merging surface 4802 extends downwardly from the merged frontsurface 50. The point of merger between the lower backrest front surface48 and the upper backrest front surface 46 is defined by a point ofinflection at the merged front surface 50. The merged front surface 50is substantially disposed in a horizontal plane 1801 (see FIGS. 18 and19). “Substantially disposed in a horizontal plane” means that themerged front surface 50 may or may not be disposed entirely in thehorizontal plane, and that if not so disposed, various portions of themerged front surface may vary from being disposed at and/or slightlyabove and/or slightly below the horizontal plane. If there is deviationfrom the horizontal plane, such deviation is minor and will not besufficiently significant so as to noticeably reduce the comfort of thechair occupant.

A portion 4604 of the merging surface 4602 extending upwardly from aportion of the merged front surface 50 (see FIG. 20D) is tangent to amerging surface plane 1003. A portion 4804 of the merging surface 4802extending downwardly from a portion of the merged front surface 50 istangent to a merging surface plane 1005. Each of the merging portions4604, 4804 is disposed in a vertical plane 1019 having a normal axis1021 which is perpendicular to the normal axis 1023 of a plane tangent1025 to the most forwardly disposed front surface 1027 of the backrestfront surface 32 (see FIGS. 20B and 20C). The plane 1803 has a frontface which defines angle θ₁ relative to and above the plane 1805 (seeFIG. 20A). The angle θ₁ is at least than 10 degrees. For example, theangle θ₁ between 10 degrees and 60 degrees. As a further example, theangle θ₁ is 30 degrees.

Where either of the merging surface portion 4604 or the merging surfaceportion 4804 is a discontinuous portion, such portion 4604 or 4804 isdefined by an imaginary planar or substantially planar surface extendingupwardly or downwardly from the merged front surface 50 and to anadjacent physical backrest front surface 32 portion (such as a vinylstrap, in the case where the backrest front surface 32 includesspaced-apart vinyl straps, as described above).

The lower backrest front surface 48 extends upwardly relative to andsubstantially from the seating surface 20 of the seat 14, and mergeswith the upper backrest front surface 46 at the merged front surface 50.“Substantially from the seating surface 20” means that the surface 48may or may not be joined to the surface 20. If the surface 48 is notjoined to the surface 20, the space between the surface 48 and thesurface 20 is relatively small and not sufficiently significant so as tonoticeably reduce the comfort of the chair occupant. For example, thespace is not so large as to permit the gluteal shelf of the chairoccupant to become wedged between surfaces 48 and 20.

The backrest surface 32 includes a top edge 47 and side edges 46 a, 46 b(see FIG. 19). The side edges 46 a, 46 b are joined by the top edge 47.It is understood that any of the top edge 47 or the side edges 46 a, 46b can be continuous or discontinuous. In this respect, any of theseedges can include discontinuous portions so long as such edges definethe perimeter of the backrest front surface 32.

A length of the backrest surface 32 is defined as any distance of thebackrest surface 32 (including any discontinuous portions of the surface46) between the merged front surface 50 and the top edge 47 and alongany vertical plane 1008 having a normal axis 1009 that is perpendicularto the normal axis 1011 of a plane 1013 tangent to the most forwardlydisposed front surface 1015 of the backrest front surface 32(see FIGS.21 and 22). A width of the backrest surface 32 is defined as anydistance of the backrest surface 32 (including any discontinuousportions of the surface 46) between the side edges 46 a, 46 b of thebackrest surface 32 and along any horizontal plane 1017 (see FIGS. 23and 24).

In the illustrated embodiment, the upper backrest front surface 46,extending from the merged front surface 50, is substantially planar.“Substantially planar” means that the upper backrest support surface 46may or may not be planar. If the surface is not planar, the deviationfrom planar is minor and not sufficiently significant to be noticeableto the chair occupant, and such deviation may be the result ofimperfections introduced during the manufacturing process of the chairor its individual components.

The upper backrest front surface 46 includes an upper backrest frontsurface portion having a minimum width and a minimum length. In thisrespect, the width and/or the length may not be the same across theentire upper backrest front surface portion but, rather, may vary from aminimum to a maximum. In the illustrated embodiment, the upper backrestfront surface portion is substantially planar and substantiallyrectangular. “Substantially rectangular” means that the upper backrestsupport surface 46 may or may not be rectangular. If the surface is notrectangular, the deviation from rectangular is minor and notsufficiently significant to be noticeable to the chair occupant, andsuch deviation may be the result of imperfections introduced during themanufacturing process of the chair or its individual components. Forexample, the upper backrest front surface portion is the upper backrestfront surface 46, and has a minimum length of at least 2 inches and aminimum width of at least 24 inches. As a further example, the minimumwidth is between 24 inches and 38 inches, and the minimum length isbetween 2 inches and 36 inches. As a further, further example, theminimum width is 26 inches and the minimum length is 12 inches.

The recessed disposition of the lower backrest front surface 48 relativeto the upper backrest front surface 46 defines a space 52 ofsubstantially the same cross-sectional area across the merged frontsupport surface 50. “Substantially the same cross-sectional area” meansthat the cross-sectional area may or may not vary by a small amountacross the merged front support surface 50. If there are variances, suchvariances are minor and will not be sufficiently significant so as tonoticeably reduce the comfort of the chair occupant.

A cross-sectional area 49 of the space 52 is defined, or is definableupon relative movement between the seat 14 and the backrest 16 (such asby tilting of the seat 14 and/or reclining of the backrest 16), in avertical plane 1019 having a normal axis 1021 which is perpendicular tothe normal axis 1023 of a plane tangent 1025 to the most forwardlydisposed front surface 1027 of the backrest front surface 32 (see FIGS.25 and 26). This cross-sectional area of the space 52 is substantiallydefined or substantially definable within the vertical plane 1019between the lower backrest front surface 48, the seating surface 20 ofthe seat 14, and a plane 1020 tangent to a respective portion (ie. thatportion disposed in the vertical plane 1019) of the upper backrest frontmerging surface 4602. Referring to FIG. 25, the plane 1020 has a frontface which defines or is positionable (by tilting of the seat 14 and/orreclining of the backrest 16) to define an angle θ₃ relative to andabove a horizontal plane 1807, and the seat 14 is positioned so as toprovide a substantially horizontal seating surface. The angle θ₃ isbetween 80 degrees and 153 degrees. In the embodiment illustrated inFIGS. 25 and 26, the angle θ₃ is 97 degrees. Where the seating surfaceportion 2001 is a discontinuous portion, the seating surface portion2001 is defined by an imaginary planar or substantially planar surfaceextending between adjacent physical seating surface portions, (such asvinyl straps, where the seating surface 20 includes spaced-apart vinylstraps, as described above). The term “substantially defined orsubstantially definable”, as used above with respect to thecross-sectional area of the space 52, means that the measurable spacebetween these components is an approximation of the actual area of thespace 52 available to receive the above-described gluteal shelf, andthat the measurable space may or may not deviate slightly from the areaof the actual space 52. If there is deviation, such deviation is minorand will not be sufficiently significant so as to reduce the comfort ofthe chair occupant. The cross-sectional area is at least 30 inches 2.For example, the cross-sectional area is between 30 inches² and 100inches². As another example, the cross-sectional area is 40 inches². Thespace 49 is provided for receiving excess flesh of a bariatric patientwho is seated in the chair.

As used herein, the term “a substantially horizontal seating surface”describes the nature of the seating surface provided by the seat 14 whenthe seat 14 is in a certain position. When a human is seated in thechair 10 when the seat 14 is in this position, the virtual plane whichintersects the body of the seated human, from the knees to the hips, ishorizontal or substantially horizontal.

One aspect of space 52 is the depth of the recess. The upper backrestfront surface 46 includes an upper front surface portion 54, and thelower backrest front surface 48 includes a lower front surface portion56. The upper front surface portion 54 of the upper backrest frontsurface 46 is disposed, or is positionable to be disposed (for example,by tilting of the seat 14 and/or reclining of the backrest 16),forwardly of the lower front surface portion 56 of the lower backrestsupport surface 48 by a horizontal distance 1039, wherein each of theupper front support surface portion 54 and the lower front surfaceportion 56 is disposed in a vertical plane 1019 having a normal axis1021 which is perpendicular to the normal axis 1023 of a plane 1025tangent to the most forwardly disposed front surface 1027 of thebackrest front surface 32 (see FIGS. 27 and 28). A plane 1041 tangent tothe portion 54 of the upper backrest front surface 46 has a front facewhich defines or is positionable (by tilting of the seat 14 and/orreclining of the backrest 16) to define an angle θ₄ relative to andabove a horizontal plane 1043 (see FIG. 29). The angle θ₄ is at least 85degrees. For example, the angle θ₄ is between 85 degrees and 120degrees. The illustrated angle θ₄ is 95 degrees (see FIG. 29). Thehorizontal distance 1039 is at least 3 inches. For example, thehorizontal distance 1039 is at least 4 inches. As a further example, thehorizontal distance 1039 is between 3 inches and 8 inches. In yet even afurther example, the horizontal distance is between 4 and 8 inches. As afurther, further example, the horizontal distance is 3 inches. The depthof the recess is characterized by the horizontal distance 1039 and isprovided for receiving excess flesh of a bariatric patient who is seatedin the chair 10.

The depth of the recess can also be defined relative to a portion of themerged front surface 50. A portion 1002 of the merged front surface 50is disposed forwardly, or is positionable to be disposed forwardly (forexample, by tilting of the seat 14 and/or reclining of the backrest 16),of a lower backrest front surface portion 56 by a horizontal distance1045, where each of the portion of the merged front surface 50 and thelower front surface portion 56 is disposed in a vertical plane 1019having a normal axis 1021 which is perpendicular to the normal axis 1023of a plane 1025 tangent to the most forwardly disposed front surface1027 of the backrest front surface 32 (see FIGS. 30 and 31). A plane1051 (in this case, plane 1051 is the same plane as plane 1025) istangent to the portion of the merged front surface 50 disposed in theplane 1019. The plane 1051 has a front face which defines or ispositionable (for example by tilting of the seat 14 and/or reclining ofthe backrest) to define an angle θ₅ relative to and above a horizontalplane 1043. The angle θ₅ is at least 80 degrees. For example, the angleθ₅ is between 80 degrees and 115 degrees. In the illustrated embodiment,θ₅ is 90 degrees (see FIG. 32). The horizontal distance 1045 is at least3 inches. For example, the distance 1045 is at least 4 inches. As afurther example, the distance 1045 is between 3 inches and 8 inches. Inyet even a further example, the horizontal distance 1045 is between 4inches and 8 inches. In a further, further example, the horizontaldistance is 3 inches.

Another aspect of this space 52 is the height of the recess. The heightof the recess is, generally, the distance between a portion 1002 of themerged front surface portion 50 and a portion 21 of the seating surface20 immediately below the merged front support surface portion 50. Thisdistance is more particularly defined as the distance 1059 between aportion 1002 of the merged front surface 50 and a portion 21 of theseating surface 20. Each of the merged front surface portion 501 and theseating surface portion 21 is disposed in a vertical plane 1019 having anormal axis 1021 which is perpendicular to the normal axis 1023 of aplane 1025 tangent to the most forwardly disposed front surface 1027(which, in this case, is the same as merged surface portion 1002) of thebackrest front surface 32 (see FIG. 34). The seating surface portion 21is also disposed in a plane 1051 tangent to the merged front surfaceportion 1002. Referring to FIG. 33, the plane 1051 (which, in this case,is the same as plane 1025) has a front face which defines or ispositionable (for example, by tilting of the seat and/or reclining ofthe backrest) to define an angle θ₂ relative to and above a horizontalplane 1075, and the seat 14 is positioned so as to provide asubstantially horizontal seating surface. The angle θ₂ is between 70degrees and 133 degrees. (see FIG. 33). In the embodiment illustrated,the angle θ₂ is 90 degrees (see FIG. 33). Where the seating surface 20includes discontinuous portions (see above), it is understood that theseating surface portion 21 may, in fact, be a discontinuous portion.Where the seating surface portion 21 is a discontinuous portion, theseating surface portion 21 is defined by an imaginary planar orsubstantially planar surface extending between adjacent physical seatingsurface portions, (such as vinyl straps, where the seating surface 20includes spaced-apart vinyl straps, as described above). For example,the distance 1059 is at least 8 inches. As a further example, thedistance 1059 is at least 10 inches. As a further, further example, thedistance 1059 is between 8 inches and 13 inches. In yet even a furtherexample, the distance 1059 is between 8 inches and 18 inches. In yeteven a further, further example, the distance 1059 is 13 inches. Themerged support surface 50 and the seating surface portion 21 are eitherspaced apart relative to one another by the distance 1059, or areindependently positionable (for example, by movement of the backrest 16or the seat 14 relative to the other, such as by tilting of the seat 14and/or reclining of the backrest 16) to become spaced apart relative toone another by the distance 1059. This aspect of the space 52 assists inproviding room for receiving excess flesh of a bariatric patient who isseated in the chair 10.

The recess extends from the merged surface portion 50 for a continuousdistance of at least 12 inches along the merged surface portion 50. Forexample, the continuous distance is 26 inches. As another example, thecontinuous distance is between 12 inches and 38 inches. In oneembodiment, the depth of the recess is substantially the same along thiscontinuous distance, and the height of the recess is substantially thesame along this continuous distance.

With respect to the depth of the recess, “substantially the same” meansthat the depth may or may not be the same along the merged front supportsurface portion. If there are differences, such differences are minorand are not sufficiently significant so as to noticeably reduce thecomfort of the chair occupant.

With respect to the height of the recess, “substantially the same” meansthat the height may or may not be the same along the merged surfaceportion. If there are differences in height, such differences are minorand are not sufficiently significant so as to noticeably reduce thecomfort of the chair occupant.

With respect to the depth of the recess along the merged front surface50, for example, the merged front surface 50 includes a merged frontsurface segment 2002. The upper backrest front merging surface 4602 ofthe upper backrest front surface extends upwardly from the merged frontsurface 50 and a lower backrest front merging surface 4802 of the lowerbackrest front surface 48 extends downwardly from the merged frontsurface 50, such that the upper backrest front surface 46 merges withthe lower backrest front surface 48 at the merged front surface 50. Eachportion of the upper backrest front merging surface 4602 is disposedwith a respective portion of the lower backrest front merging surface4802 in a respective vertical plane 5000, wherein the respectivevertical plane 5000 has a respective vertical plane normal axis 5002which is perpendicular to the normal axis 1023 of the plane 1025 tangentto the most forwardly disposed front surface 1027 of the backrest frontsurface 32. Each portion of the upper backrest front merging surface istangent to a respective upper backrest front merging surface plane andthe respective portion of the lower backrest front merging surface istangent to a respective lower backrest front merging surface plane. Therespective upper backrest front merging surface plane has a front facewhich defines an angle θ₆ relative to and above the respective lowerbackrest front merging surface portion plane, wherein the angle θ₆ is atleast 10 degrees. For example, the angle θ₆ is between 10 degrees and 60degrees. As a further example, θ₆ is 30 degrees. Each portion of themerged front surface segment 2002 is disposed with a respective portionof the lower backrest front surface 48 in a respective one of thevertical planes 5000. Each portion of the merged front surface segmentis tangent to a respective merged front surface segment portion plane,wherein the merged front surface segment portion plane has a front facewhich defines or is positionable (by seat tilt and/or back recline) todefine an angle θ₇ relative to and above a horizontal plane, wherein θ₇is at least 80 degrees, such as 90 degrees. For example, θ₇ is between80 degrees and 115 degrees. Each portion of the merged front surfacesegment 2002 is disposed forwardly, or is positionable to be disposed(for example by tilting of the seat 14 and/or reclining of the backrest16) forwardly, of the respective portion of the lower backrest frontsurface 48 by a horizontal distance 6000 of at least 3 inches. Forexample, the horizontal distance 6000 is between 3 inches and 8 inches.As a further example, the horizontal distance 6000 is at least 4 inches,such as between 4 inches and 8 inches. As a further, further example,the horizontal distance 6000 is 3 inches. The segment 2002 has a width6002 of at least 12 inches. For example, the width 6002 of the segment2002 is 26 inches. As another example, the width 6002 of the segment2002 is between 12 inches and 38 inches.

For example, with respect to the depth along the merged front surfacesegment 2002 having portions 2004, 2006 in respective vertical planes5102, 5202 (vertical planes 5000 include planes 5102, 5202), andreferring to FIGS. 35 to 39, each of portions 4604, 4606 of the upperbackrest front merging surface 4602 is disposed with a respectiveportion 4804, 4806 of the lower backrest front merging surface 4802 in arespective one of the vertical planes 5102, 5202 (see FIGS. 35 and 36),wherein each of the respective vertical planes 5102, 5202 has arespective vertical plane normal axis 5104, 5204 which is perpendicularto the normal axis 1023 of the plane 1025 tangent to the most forwardlydisposed front surface 1027 of the backrest front surface 32 (see FIG.36). Each of the portions 4604, 4606 is tangent to a respective upperbackrest front merging surface plane 4608, 4610 (in this case, planes4608 and 4610 are the same), and each of the portions 4804, 4806 istangent to a respective lower backrest front merging surface plane 4808,4810 (in this case, planes 4808, 4810 are the same). Referring to FIG.37, the respective upper backrest front merging surface portion plane4608, 4610 has a front face which defines an angle θ₆ relative to andabove the respective lower backrest front merging surface portion plane4808, 4810, wherein the angle θ₆ is greater than 10 degrees. In FIG. 37,the angle θ₆ is 30 degrees. Each portion 2004, 2006 of the merged frontsurface segment 2002 is disposed with a respective portion 4812, 4814 ofthe lower backrest front surface in a respective one of the verticalplanes 5102, 5202. Referring to FIG. 38, each portion 2004, 2006 (onlyportion 2006 is shown in FIG. 38) is tangent to a respective mergedfront surface segment plane 2018 a, 2018 b (only plane 2018 b is shownin FIG. 38). The respective merged front surface segment portion plane(ie. plane 2018 b) has a front face which defines or is positionable(for example, by seat tilt and/or back recline) to define an angle θ₇relative to and above the horizontal plane 2020 which is greater than 80degrees, such as 90 degrees (shown). Referring to FIG. 39, each portion2004, 2006 is disposed or is positionable to be disposed (for example bytilting of the seat 14 and/or reclining of the backrest 16) forwardly,of the respective portion 4812, 4814 (only portion 4814 is shown in FIG.39) of the lower backrest front surface 48 by a horizontal distance 6000of at least 3 inches.

With respect to the height of the recess across the merged front surfacesegment 2002, each portion of the merged front surface segment 2002 isdisposed, or is positionable to be disposed (for example, by tilting ofthe seat 14, or reclining of the backrest 16), above a respectiveportion of the seating surface 20 by a vertical distance of at least 8inches, wherein each portion of the merged front surface segment 2002and the respective seating surface portion is disposed in a respectiveone of the vertical planes 5000. For example, the vertical distance isbetween 8 inches and 18 inches. As a further example, the verticaldistance is 10 inches. Each portion of the merged front segment 2002 istangent to a respective merged front segment portion plane. Therespective seating surface portion 20 is also disposed in the respectivemerged front surface segment plane. The respective merged front surfacesegment plane has a front face which defines or is positionable (by seattilt and/or back recline) to define an angle θ₈ relative to and above ahorizontal plane, where the angle θ₈ is between 70 degrees and 133degrees, and the seat 14 is positioned so as to provide a substantiallyhorizontal seating surface.

For example, with respect to the height of the recess across the mergedfront support surface segment 2002 having portions 2004, 2006 in thevertical planes 5102, 5104 (vertical planes 5000 include planes 5102,5104), and referring to FIGS. 35 and 40, each portion 2004, 2006 (onlyportion 2006 is shown in FIG. 40) of the merged front surface segment2002 is disposed, or is positionable to be disposed (for example, bytilting of the seat 14, or reclining of the backrest 16), above arespective portion 2202, 2204 (only portion 2204 is shown in FIG. 40) ofthe seating surface 20 by a vertical distance 6002 of at least 8 inches,wherein each portion 2004, 2006 of the merged front surface segment 2002and the respective seating surface portion 2202, 2204 is disposed in arespective one of the vertical planes 5102, 5202 (see FIG. 35). Eachportion 2004, 2006 is tangent to a respective merged front surfacesegment portion plane 2018 a, 2018 b. The respective seating surfaceportion 2202, 2204 is also disposed in the respective merged frontsurface segment plane 2018 a, 2018 b (only plane 2018 b is shown in FIG.40, and this is tangent to portion 2006). Referring to FIG. 40, therespective merged front surface segment plane 2018 a, 2018 b has a frontface which defines or is positionable (by seat tilt and/or back recline)to define the angle θ₈ relative to and above the horizontal plane 2020,wherein the angle θ₈ is between 70 degrees and 133 degrees, and the seat14 is positioned so as to provide a substantially horizontal seatingsurface. In FIG. 40, angle θ₈ is 90 degrees.

With respect to the cross-sectional area of the space of the recessacross the merged front surface segment 2002, in each of the verticalplanes 5000, a respective two-dimensional space is disposed in therespective vertical plane and is defined, or is definable uponpositioning of the seat 14 relative to the backrest 16 (for example, bytilting of the seat 14 and/or reclining of the backrest 16), between:(i) the lower backrest front surface 48, (ii) the seating surface 20,and (iii) the respective upper backrest front surface merging portionplane (which is tangent to the upper backrest front surface mergingportion disposed in the respective vertical plane 5000). The respectiveupper backrest front surface merging portion plane has a front facewhich defines or is positionable (by seat tilt and/or back recline) todefine an angle θ₉ relative to and above a horizontal plane, wherein theangle θ₉ is between 80 degrees and 153 degrees, and the seat 14 ispositioned so as to provide a substantially horizontal seating surface.The space has an area of at least 30 inches². For example, the space isbetween 30 inches² and 100 inches². As a further example, the space is40 inches².

For example, with respect to the cross-sectional area 4900 of the spaceof the recess across the merged front surface segment 2002 having theportions 2002, 2004 in the vertical planes 5102, 5104 (vertical planes5000 include planes 5102, 5104), and referring to FIGS. 35 and 41, arespective two-dimensional space is disposed in the respective verticalplane and is defined, or is definable upon positioning of the seat 14relative to the backrest 16 (for example, by tilting of the seat 14and/or reclining of the backrest 16), between: (i) the lower backrestfront surface 48, (ii) the seating surface 20, and (iii) a respectiveupper backrest front surface merging portion plane 4608, 4610 (onlyplane 4610 is illustrated in FIG. 41, see also FIG. 35). Referring toFIG. 41, the respective upper backrest front surface merging portionplane 4608, 4610 has a front face which defines or is positionable (byseat tilt and/or back recline) to define the angle θ₉ to and above thehorizontal plane 2028, wherein the angle θ₉ is between 80 degrees and153 degrees, and the seat 14 is positioned so as to provide asubstantially horizontal seating surface. In FIG. 41, the illustratedangle θ₉ is 97 degrees.

Optionally, a headrest 3000 may be provided, and releasably coupled tothe backrest frame 30. The headrest is single axis height adjustablewith the option of either a formed acrylonitrile-butadiene-styrene (ABS)head support or a contoured closed cell polyurethane foam head support.

The legrest 300 is pivotally mounted to the seat frame 18 at the posts82 a, 82 b (see above discussion). The legrest 300 includes a legsupport member 302 and a foot support member 304. The leg support member302 depends downwardly from the posts 82 a, 82 b and is configured tosupport the calves of the occupant of the chair 10. The foot supportmember 304 extends forwardly from the leg support member 302 and isconfigured to support the feet of the occupant of the chair 10. Thelegrest 300 is moveable by and supported in an elevated position by apair of extendible/retractable members 306 a, 306 b, similar to theextendible/retractable members 204 a, 204 b, but cab be rated with alower exertion force. Each of the extendible/retractable members 306 a,306 b is pivotally coupled at one end to the legrest 300. In particular,each of the members 306 a, 306 b is coupled to a respective one of thearms 308 a, 308 b extending rearwardly from the leg support member 302of the legrest 300 by a respective bolt extending through a respectivepair of aligned apertures, one of the respective pair of alignedapertures being provided in a respective one of the members 306 a, 306 band the other of the respective pair of aligned apertures being providedin a respective one of the arms 308 a, 308 b. Each of the members 306 a,306 b is also pivotally coupled at a second opposite end to the chairframe 14. In particular, the second end of each of the members 306 a,306 b is pivotally coupled to a respective one of the pairs of forks 94a, 95 a and 94 b, 95 b (see FIGS. 1, 2, and 4) by a respective boltextending through a respective set of three aligned apertures, one ofthe respective pair of aligned apertures being provided in a respectiveone of the members 306 a, 306 b and the other two being provided in eachof a respective one of the pairs of forks 94 a, 95 a, and 94 b, 95 b.

The members 306 a, 306 b enable positioning and support of legrest 300.Extension of the members 306 a, 306 b urges the legrest 300 to rotate inan upwardly and forwardly direction, causing elevation of the feet of anoccupant of the chair 10, and also causing extension of the calves of anoccupant of the chair.

A hand actuator 310 is mounted to the lower rail 93 a, and coupled tothe extendible/retractable members 204 a, 204 b, to effect unlocking ofthe extendible/retractible members 204 a, 204 b, and thereby effectpivotal movement of the legrest between various elevated andnon-elevated positions. Operation of hand actuator 310 to effectactuation of the members 204 a, 204 b is similar to the operation ofactuators 201 a, 201 b.

The chair 10 of the present invention is particularly useful for seatingof bariatric patients. In this respect, any of the above-describedembodiments of the chair 10 can be used for the seating of personshaving a body weight of at least 300 pounds.

Although the disclosure describes and illustrates preferred embodimentsof the invention, it is to be understood that the invention is notlimited to these particular embodiments. Many variations andmodifications may occur to those skilled in the art within the scope ofthe invention. For definition of the invention, reference is to be madeto the appended claims.

1. A chair comprising: a base frame; a seat coupled to the base frameand including a seating surface; and a backrest coupled to either thebase frame or the seat, including a backrest front surface, the backrestfront surface including: an upper backrest front surface including anupper backrest front surface portion; and a lower backrest front surfaceincluding a lower backrest front surface portion; wherein the upperbackrest front surface portion is disposed, or is positionable to bedisposed, forwardly of the lower backrest front surface portion by ahorizontal distance of at least 3 inches; and wherein each of the upperbackrest front surface portion and the lower backrest front surfaceportion is disposed in a vertical plane having a vertical plane normalaxis which is perpendicular to a normal axis of a plane tangent to themost forwardly disposed front surface of the backrest front surface. 2.The chair as claimed in claim 1, wherein the horizontal distance isbetween 3 inches and 8 inches.
 3. The chair as claimed in claim 1,wherein the horizontal distance is at least 4 inches.
 4. The chair asclaimed in claim 3, wherein the horizontal distance is between 4 inchesand 8 inches.
 5. The chair as claimed in claim 1, wherein the seat has aminimum width of at least 18 inches.
 6. The chair as claimed in claim 5,wherein the minimum width of the seat is between 18 inches and 38 inches7. The chair as claimed in claim 5, wherein the seat has a minimumlength of at least 20 inches.
 8. The chair as claimed in claim 7,wherein the seat has a minimum length of between 16 inches and 24inches.
 9. The chair as claimed in claim 1, wherein an upper backrestfront surface portion plane is tangent to the upper backrest frontsurface portion, and wherein the upper backrest front surface portionplane has a front face which defines or is positionable to define anangle relative to and above a horizontal plane, wherein the angle is atleast 85 degrees.
 10. The chair as claimed in claim 9, wherein the angleis between 85 degrees and 120 degrees.
 11. The chair as claimed in claim9 wherein the angle is 95 degrees.
 12. The chair as claimed in claim 5,wherein the backrest has a minimum width of at least 24 inches.
 13. Thechair as claimed in claim 11, wherein the backrest has a minimum widthof between 24 inches and 36 inches.
 14. The chair as claimed in claim 3,wherein the backrest has a minimum width of at least 24 inches.
 15. Thechair as claimed in claim 1, wherein the backrest has a minimum width ofat least 24 inches.
 16. The chair as claimed in claim 15, wherein thebackrest has a minimum width of between 24 inches and 36 inches.
 17. Achair comprising: a base frame; a seat coupled to the base frame andincluding a seating surface; and a backrest coupled to either the baseframe or the seat, including a backrest front surface, the backrestfront surface including: an upper backrest including an upper backrestfront surface having an upper backrest front surface segment, whereinthe upper backrest front surface segment has a width of at least 24inches; and a lower backrest including a lower backrest front surface;wherein each portion of the upper backrest front surface segment isdisposed with a respective portion of the lower backrest front surfacein a respective vertical plane having a vertical plane normal axis whichis perpendicular to a normal axis of a plane tangent to the mostforwardly disposed front surface of the backrest front surface; andwherein each portion of the upper backrest surface segment is alsodisposed, or is positionable to be disposed, forwardly of the respectiveportion of the lower backrest front surface by a horizontal distance ofat least 3 inches.
 18. The chair as claimed in claim 17, wherein thehorizontal distance is between 3 inches and 8 inches.
 19. The chair asclaimed in claim 17, wherein the horizontal distance is at least 4inches.
 20. The chair as claimed in claim 19, wherein the horizontaldistance is between 4 inches and 8 inches.
 21. The chair as claimed inclaim 17, wherein the seat has a minimum width of at least 18 inches.22. The chair as claimed in claim 21, wherein the seat has a minimumwidth between 18 inches and 38 inches
 23. The chair as claimed in claim21, wherein the seat has a minimum length of at least 20 inches.
 24. Thechair as claimed in claim 23, wherein the seat has a minimum length ofbetween 16 inches and 24 inches.
 25. The chair as claimed in claim 23,wherein the backrest has a minimum width of at least 6 inches.
 26. Thechair as claimed in claim 25, wherein the backrest has a minimum widthof at least 24 inches.
 27. The chair as claimed in claim 26, wherein thebackrest has a minimum width of between 24 inches and 38 inches.
 28. Thechair as claimed in claim 25, wherein the backrest has a minimum lengthof at least 2 inches.
 29. The chair as claimed in claim 17, wherein thebackrest has a minimum width of at least 24 inches.
 30. The chair asclaimed in claim 17, wherein each portion of the upper backrest frontsurface segment is tangent to a respective upper backrest front surfacesegment portion plane, and wherein the respective upper backrest frontsurface segment portion plane has a front face which defines or ispositionable to define an angle relative to and above a horizontalplane, wherein the angle is at least 85 degrees.
 31. The chair asclaimed in claim 30, wherein the angle is between 85 degrees and 120degrees.
 32. The chair as claimed in claim 30, wherein the angle is 95degrees.
 33. A chair comprising: a base frame; a seat coupled to thebase frame and including a seating surface; and a backrest coupled toeither the base frame or the seat, including a backrest front surface,the backrest front surface including: an upper backrest front surface; alower backrest front surface; and a merged front surface, wherein anupper backrest front merging surface of the upper backrest front surfaceextends upwardly from the merged front surface, and a lower backrestfront merging surface of the lower backrest front surface extendsdownwardly from the merged front surface such that the upper backrestfront surface merges with the lower backrest front surface at the mergedfront surface; wherein each of a portion of the upper backrest frontmerging surface, a portion of the merged front surface, and a portion ofthe lower backrest front merging surface is disposed in a vertical planehaving a vertical plane normal axis which is perpendicular to a normalaxis of a plane tangent to the most forwardly disposed front surface ofthe backrest front surface; and wherein an upper backrest front mergingsurface portion plane is tangent to the upper backrest front mergingsurface portion and a lower backrest front merging surface portion planeis tangent to the lower backrest front merging surface portion, whereinthe upper backrest front merging surface portion plane has a front facewhich defines a first angle relative to and above the lower backrestfront merging surface portion plane, wherein the first angle is at least10 degrees, and wherein the merged front surface portion is disposedforwardly, or is positionable to be disposed forwardly, of a portion ofthe lower backrest front surface by a horizontal distance of at least 3inches, wherein the lower backrest front surface portion is disposed inthe vertical plane.
 34. The chair as claimed in claim 33, wherein thefirst angle is between 10 degrees and 60 degrees.
 35. The chair asclaimed in claim 33, wherein a merged front surface portion plane istangent to the merged front surface portion, and wherein the mergedfront surface portion plane has a front face which defines or ispositionable to define a second angle relative to and above a horizontalplane, wherein the second angle is at least 80 degrees.
 36. The chair asclaimed in claim 33, wherein the horizontal distance is between 3 inchesand 8 inches.
 37. The chair as claimed in claim 33, wherein thehorizontal distance is at least 4 inches.
 38. The chair as claimed inclaim 37, wherein the horizontal distance is between 4 inches and 8inches.
 39. The chair as claimed in claim 33, wherein the seat has aminimum width of at least 18 inches.
 40. The chair as claimed in claim39, wherein the seat has a minimum width of between 18 inches and 38inches
 41. The chair as claimed in claim 39, wherein the seat has aminimum length of at least 20 inches.
 42. The chair as claimed in claim41, wherein the seat has a minimum length of between 16 inches and 24inches.
 43. The chair as claimed in claim 34, wherein the backrest has aminimum width of at least 24 inches.
 44. The chair as claimed in claim39, wherein the backrest has a minimum width of at least 24 inches. 45.The chair as claimed in claim 44, wherein the backrest has a minimumwidth of between 24 inches and 36 inches.
 46. The chair as claimed inclaim 43, wherein the backrest has a minimum length of at least 2inches.
 47. The chair as claimed in claim 46, wherein the backrest has aminimum length of at least 6 inches.
 48. The chair as claimed in claim33, wherein the backrest has a minimum width of at least 24 inches. 49.The chair as claimed in claim 35, wherein the second angle is between 80degrees and 115 degrees.
 50. The chair as claimed in claim 35, whereinthe second angle is 90 degrees.
 51. The chair as claimed in claim 33,wherein the merged front surface portion is disposed, or is positionableto be disposed, above a seating surface portion of the seating surfaceby a vertical distance of at least 8 inches, wherein the seating surfaceportion is disposed in the vertical plane and is also disposed in amerged front surface portion plane tangent to the merged front surfaceportion.
 52. The chair as claimed in claim 51, wherein the seat ispositioned so as to provide a substantially horizontal seating surface,and wherein the merged front surface portion plane has a front facewhich defines or is positionable to define a third angle relative to andabove a horizontal plane, wherein the third angle is between 70 degreesand 133 degrees.
 53. The chair as claimed in claim 51, wherein thedistance by which the merged front surface portion is disposed, or ispositionable to be disposed, above the seating surface portion of theseating surface is between 8 inches and 18 inches.
 54. The chair asclaimed in claim 51, wherein the distance by which the merged frontsurface portion is disposed, or is positionable to be disposed, abovethe seating surface portion of the seating surface is at least 10inches.
 55. The chair as claimed in claim 33, wherein a two-dimensionalspace is disposed in the vertical plane and is defined or definablebetween: (i) the lower backrest front surface, (ii) the seating surface,and (iii) the upper backrest front merging surface portion plane, suchthat the space has an area of at least 30 inches².
 56. The chair asclaimed in claim 55, wherein the area of the space is between 30 inches²and 100 inches².
 57. The chair as claimed in claim 55, wherein the seatis positioned so as to provide a substantially horizontal seatingsurface, and wherein the upper backrest front merging surface portionplane has a front face which defines or is positionable to define afourth angle relative to and above a horizontal plane, wherein thefourth angle is between 80 degrees and 153 degrees.
 58. A chaircomprising: a base frame; a seat coupled to the base frame and includinga seating surface; and a backrest coupled to either the base frame orthe seat, including a backrest front surface, the backrest front surfaceincluding: an upper backrest front surface; a lower backrest frontsurface; and a merged front surface including a merged front surfacesegment, wherein an upper backrest front merging surface of the upperbackrest front surface extends upwardly from the merged front surfaceand a lower backrest front merging surface of the lower backrest frontsurface extends downwardly from the merged front surface, such that theupper backrest front surface merges with the lower backrest frontsurface at the merged front surface; wherein each portion of the mergedfront surface segment is disposed with a respective portion of the lowerbackrest front merging surface and with a respective portion of theupper backrest front merging surface in a respective vertical plane, andwherein the respective vertical plane has a respective vertical planenormal axis which is perpendicular to a normal axis of a plane tangentto the most forwardly disposed front surface of the backrest frontsurface; and wherein the respective portion of the upper backrest frontmerging surface is tangent to a respective upper backrest front mergingsurface portion plane and the respective portion of the lower backrestfront merging surface is tangent to a respective lower backrest frontmerging surface portion plane, wherein the respective upper backrestfront merging surface portion plane has a front face which defines afirst angle relative to and above the respective lower backrest frontmerging surface portion plane, wherein the first angle is at least 10degrees; and wherein each portion of the merged front surface segment isdisposed forwardly, or is positionable to be disposed forwardly, of arespective portion of the lower backrest front surface by a horizontaldistance of at least 3 inches, wherein the respective lower backrestfront surface portion is disposed in the respective vertical plane; andwherein the merged front surface segment has a width of at least 24inches.
 59. The chair as claimed in claim 58, wherein each portion ofthe merged front surface segment is tangent to a respective merged frontsurface segment portion plane, and wherein the respective merged frontsurface segment portion plane has a front face which defines or ispositionable to define a second angle relative to and above a horizontalplane, wherein the second angle is greater than 80 degrees.
 60. A chaircomprising: a base frame; a seat coupled to the base frame and includinga seating surface; and a backrest coupled to either the base frame orthe seat, including a backrest front surface, the backrest front surfaceincluding: an upper backrest front surface; a lower backrest frontsurface; and a merged front surface, wherein the lower backrest frontsurface merges with the upper backrest front surface at the merged frontsurface; wherein a merging surface portion of the upper backrest frontsurface extends upwardly from a portion of the merged front surface, anda merging surface portion of the lower backrest front surface extendsdownwardly from the merged front surface portion, and wherein each ofthe upper backrest front merging surface portion, the merged frontsurface portion, and the lower backrest front merging surface portion isdisposed in a vertical plane having a vertical plane normal axis whichis perpendicular to a normal axis of a plane tangent to the mostforwardly disposed front surface of the backrest front surface; whereinan upper backrest front merging surface portion plane is tangent to theupper backrest front surface merging portion and a lower backrest frontmerging surface portion plane is tangent to the lower backrest frontsurface merging portion, wherein the upper backrest front mergingsurface portion plane has a front face which defines a first anglerelative to and above the lower backrest front merging surface portionplane, wherein the first angle is at least 10 degrees; and wherein amerged front surface portion plane is tangent to the merged frontsurface portion; and wherein the merged front surface portion isdisposed, or is positionable to be disposed, above a seating surfaceportion of the seating surface by a distance of at least 8 inches,wherein the seating surface portion is disposed in the vertical planeand is also disposed in the merged front surface portion plane.
 61. Thechair as claimed in claim 60, wherein the seat is positioned so as toprovide a substantially horizontal seating surface, and wherein themerged front surface portion plane has a front face which defines or ispositionable to define a second angle relative to and above a horizontalplane, wherein the second angle is between 70 degrees and 133 degrees.62. A chair comprising: a base frame; a seat coupled to the base frameand including a seating surface; and a backrest coupled to either thebase frame or the seat, including a backrest front surface, the backrestfront surface including: an upper backrest front surface; a lowerbackrest front surface; and a merged front surface, wherein the lowerbackrest front surface merges with the upper backrest front surface atthe merged front surface, and wherein a merging surface portion of theupper backrest front surface extends upwardly from a portion of themerged front surface, and a merging surface portion of the lowerbackrest front surface extends downwardly from the merged front surfaceportion; and wherein each of the upper backrest front merging surfaceportion, the merged front surface portion, and the lower backrest frontmerging surface portion is disposed in a vertical plane having avertical plane normal axis which is perpendicular to a normal axis of aplane tangent to the most forwardly disposed front surface of thebackrest front surface; and wherein an upper backrest front mergingsurface portion plane is tangent to the upper backrest front mergingsurface portion and a lower backrest front merging surface portion planeis tangent to the lower backrest front merging surface portion, whereinthe upper backrest front merging surface portion plane has a front facewhich defines a first angle relative to and above the lower backrestfront merging surface portion plane, wherein the first angle is at least10 degrees, and wherein a two-dimensional space is disposed in thevertical plane and is defined or is definable between: (i) the lowerbackrest front surface, (ii) the seating surface, and (iii) the upperbackrest front merging surface portion plane, such that the space has anarea of at least 30 inches².
 63. The chair as claimed in claim 62,wherein the seat is positioned so as to provide a substantiallyhorizontal seating surface, and wherein the upper backrest front mergingsurface portion plane has a front face which defines or is positionableto define a second angle relative to and above a horizontal plane,wherein the second angle is between 80 degrees and 153 degrees.
 64. Achair comprising: a base frame; a seat coupled to the base frame andincluding a seating surface; and a backrest coupled to either the baseframe or the seat, including a backrest front surface, the backrestfront surface including: an upper backrest front surface; a lowerbackrest front surface; and a merged front surface including a mergedfront surface segment, wherein an upper backrest front merging surfaceof the upper backrest front surface extends upwardly from the mergedfront surface and a lower backrest front merging surface of the lowerbackrest front surface extends downwardly from the merged front surface,such that the upper backrest front surface merges with the lowerbackrest front surface at the merged front surface; wherein each portionof the merged front surface segment is disposed with a respectiveportion of the lower backrest front merging surface and with arespective portion of the upper backrest front merging surface in arespective vertical plane, wherein the respective vertical plane has arespective vertical plane normal axis which is perpendicular to a normalaxis of a plane tangent to the most forwardly disposed front surface ofthe backrest front surface; and wherein the respective portion of theupper backrest front merging surface is tangent to a respective upperbackrest front surface merging portion plane and the respective portionof the lower backrest front merging surface is tangent to a respectivelower backrest front surface merging portion plane; and wherein therespective upper backrest front merging surface portion plane has afront face which defines a first angle relative to and above therespective lower backrest front merging surface portion plane, whereinthe first angle is at least 10 degrees; and wherein each portion of themerged front surface segment is tangent to a respective merged frontsurface segment portion plane; and wherein each portion of the mergedfront surface segment is disposed, or is positionable to be disposed,above a respective seating surface portion by a distance of at least 8inches, and wherein the respective seating surface portion is disposedin the respective vertical plane and is also disposed in the respectivemerged front surface segment portion plane; and wherein the merged frontsurface segment has a width of at least 24 inches.
 65. The chair asclaimed in claim 64, wherein the seat is positioned so as to provide asubstantially horizontal seating surface, and wherein the respectivemerged front surface segment portion plane has a front face whichdefines or is positionable to define a second angle relative to andabove a horizontal plane, wherein the second angle is between 70 degreesand 133 degrees.
 66. The chair as claimed in claim 64, wherein eachportion of the merged front surface segment is disposed forwardly, or ispositionable to be disposed forwardly, of a respective portion of thelower backrest front surface by a horizontal distance of at least 3inches, wherein the respective portion of the lower backrest frontsurface is disposed in the respective vertical plane.
 67. The chair asclaimed in claim 64, wherein a two dimensional space is disposed in therespective vertical plane and is defined or is definable between: (i)the lower backrest front surface, (ii) the seating surface, and (iii)the respective upper backrest front merging surface portion plane, suchthat the space has an area of at least 30 inches².
 68. A chaircomprising: a base frame; a seat coupled to the base frame and includinga seating surface; and a backrest coupled to either the base frame orthe seat, including a backrest front surface, the backrest front surfaceincluding: an upper backrest front surface; and a lower backrest frontsurface; a merged front surface including a merged front surfacesegment, wherein an upper backrest front merging surface of the upperbackrest front surface extends upwardly from the merged front surfaceand a lower backrest front merging surface of the lower backrest frontsurface extends downwardly from the merged front surface, such that theupper backrest front surface merges with the lower backrest frontsurface at the merged front surface; wherein each portion of the mergedfront surface segment is disposed with a respective portion of the lowerbackrest front merging surface and with a respective portion of theupper backrest front merging surface in a respective vertical plane,wherein the respective vertical plane has a respective vertical planenormal axis which is perpendicular to a normal axis of a plane tangentto the most forwardly disposed front surface of the backrest frontsurface; and wherein the respective portion of the upper backrest frontmerging surface is tangent to a respective upper backrest front mergingsurface portion plane and the respective portion of the lower backrestfront merging surface is tangent to a respective lower backrest frontmerging surface portion plane, wherein the respective upper backrestfront merging surface portion plane has a front face which defines afirst angle relative to and above the respective lower backrest frontmerging surface portion plane, wherein the first angle is at least 10degrees; and wherein, a two-dimensional space is disposed in therespective vertical plane and is defined or is definable between: (i)the lower backrest front surface, (ii) the seating surface, and (iii)the respective upper backrest front merging surface portion plane, suchthat the space has an area of at least 30 inches², and wherein themerged front surface segment has a width of at least 24 inches.
 69. Thechair as claimed in claim 68, wherein the seat is positioned so as toprovide a substantially horizontal seating surface and wherein therespective upper backrest front merging surface portion plane has afront face which defines or is positionable to define a second anglerelative to and above a horizontal plane, wherein the second angle isbetween 80 degrees and 153 degrees.